CA1242362A

CA1242362A - Aramid fibre-polymer mixtures and process for production

Info

Publication number: CA1242362A
Application number: CA000447552A
Authority: CA
Inventors: Douglas C. Edwards; James A. Crossman
Original assignee: Polysar Ltd
Current assignee: Polysar Ltd
Priority date: 1983-04-19
Filing date: 1984-02-15
Publication date: 1988-09-27
Also published as: DE3413884C2; JPH0460141B2; IT8467394A0; IT1178922B; GB2138430A; DE3413884A1; IT8467394A1; FR2544727B1; FR2544727A1; GB2138430B; AU2686384A; JPS59199231A; AU572504B2

Abstract

ARAMID FIBRE-POLYMER MIXTURES
AND PROCESS FOR PRODUCTION
Abstract of the Disclosure A process for producing mixtures of polymer and aramid fibre comprises the steps of providing an agitated aqueous solution of coagulant for the polymer, adding an aqueous suspension of the aramid fibrous material to the coagulant solution, adding the polymer in aqueous latex form to the coagulant solution and co-coagulating the polymer and aramid fibrous material, and recovering and drying the mixture of polymer and aramid fibrous material.

Description

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FIELD OF THE INVENTION
Tbe present invention is directed to a ~rocesD of producing mixtures of polymers and fibrOus~Raterials-~3 tbe products of said process and to tbe vulcanizates obtained from such products.
DESCRIPTION OF THE PRIOR ART
A great variety of materials are known in the art for use as fillers and/or reinforcing materials for plastics and for rubbers. Fillers are normally considered to be largely non reinforcing and are usually selected from the particulate inorganic compounds. Reinforcing materials are usually selected from the particulate carbon blacks and certain particulate inorganic compounds.
Fibrous materials frequently are added to rubber compounds to improve various properties in rubbers and to reduce the extent of fabric reinforcement and suitable sucb fibres include asbestos, cellulose fibres, glass fires, cotton and various synthetic organic fibres sucb as polyester and rayon. Tbe fibre may be used as sbort fibres, for example cbopped fibres, or as longer fibres. An important facet of tbe use of sucb fibres is tbe incorporation of tbe fibres into the polymer matrix.
It is well known that carbon black may be incorporated into polymers by mixing, particularly as a suspension in water, wit a polymer in latex form and coagulating tbe mixture, see for example U.S. Patents 1,991,367, 2,419,512 and 2,441,090. U.S. Patent 4,263,184 discloses a bomogeneous predispersed fibre composition prepared by mixing a latex of a polymer with fibrous material to form a wetted fibre mixture and a coagulant is mixed~witb tbe wetted fibre mixture to form tbe predispersed fibre composition.
SUMMARY OF THE INVENTION
; The present invention Is directed to a process

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for the production of mixtures of polymer and fibrous materials, said process comprising tbe steps of providing an agitated aqueous solution of coagulant for tbe polymer, adding an aqueous suspension of said fibrous material to toe coagulant solution, adding said polymer in aqueous latex form to said coagulant solution and co-coagulating said polymer and fibrous material, and recovering and drying the mixture of polymer and fibrous material.
Toe invention is further directed to a process for tbe production of mixtures of polymer and fibrous materials, said process comprising the steps of providing an agitated aqueous solution of coagulant for the polymer, adding an aqueous suspension of said fibrous material to the coagulant solution, adding said polymer in aqueous latex form to said coagulant solution and co-coagulating said polymer and fibrous material, and recovering and drying tbe mixture of polymer and fibrous material, said fibrous material being a polymeric paraphenylene : terepbthalamide aramid having an average lengtb of from about 1 to about 5 mm and a BET surface area of greater : tban 1 m2/g.
Toe invention is further directed to polymer-; fibrous material mixtures produced by the process comprising the steps of providing an agitated aqueous solution of coagulant for the polymer, adding an aqueous suspension of said fibrous material to tbe coagulant solution, adding said polymer in aqueous late form to said coagulant solution and co-coagulating said polymer and fibrous material, and recovering and drying tbe : 30 mixture of polymer and fibrous material.
The invention is furtber directed to polymer-- fibrous material mixtures produced by the process comprising toe steps of providing an agitated aqueous ~;~ solution of coagulant for the polymer, adding an aqueous ;, -' ~23tS~

suspension of said fibrous material to the coagulant solution, adding said polymer in aqueous latex form to said coagulation solution and co-coagulating said polymer and fibrous material, and recovering and drying toe mixture of polymer and fibrous material, said fibrous material being a polymeric parapbenylene terephtbalamide aramid having an average length of from about 1 co about 5 mm and a BET surface area of greater than 1 m2/g.
The invention is further directed to vulcanizates produced from toe mixture of polymer and fibrous material produced by tbe process comprising the steps of providing an agitated aqueous solution of coagulant for toe polymer, adding an aqueous suspension of said fibrous macerial to the coagulant solution, adding said polymer in aqueous latex form to said coagulant solution and co-coagulating said polymer and fibrous material, and recovering and drying the mixture of polymer and fibrous material, by the steps comprising mixing said mixture of polymer and fibrous material witb rubber compounding ingredients and vulcanization active agents, soaping the so-formed mixture and vulcanizing the shaped mixture by heating a an elevated temperature.
Tbe invention is further directed to vulcanizates produced from the mixture of polymer and fibrous material produced by tbe process comprising toe steps of providing an agitated aqueous solution of coagulant for the polymer, adding an aqueous suspension of said fibrous material to toe coagulant solution, adding said polymer in aque`ous latex form to said coagulation solution and co-coagulating said polymer and fibrous material, and recovering and drying tbe mixture of polymer and fibrous material, said fibrous material being a polymeric paraphenylene terepbthalamide aramid waving an average length of from about 1 to about 5 mm and a BET surface area of greater .

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tban 1 m2/g, by the steps comprising mixing said mixture of polymer and fibrous material with rubber compounding ingredients and vulcanization active agents, shaping the so-formed mixture and vulcanizing the sbaped mixture by beating at an elevated temperature.
The invention is furtber directed to vulcanizaces produced from the mixture of polymer and fibrous material produced by the process comprising tbe steps of providing an agitated aqueous solution of coagulant for the polymer, adding an aqueous supension of said fibrous material to the coagulant solution, adding said polymer in aqueous latex form to said coagulant solution and co-coagulating said polymer and said fibrous material, and recovering and drying the mixture of polymer and fibrous material, said fibrous material being a polymeric paraphenylene terephtbalamide aramid having an average length of from about 1 to about 5 mm and a BET surface area of greater than 1 m2/g, by tbe steps comprising mixing said mixture of polymer and fibrous material with one or more compatible polymers, with rubber compounding ingredients and vulcanization active agents, shaping the so-formed mixture and vulcanizing the shaped mixture by beating at an elevated temperature.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The polymers which may be used in this invention are selected from natural rubber in latex form and the synthetic rubbery polymers normally produced by emulsion polymerization and available in the latex form sucb as :: styrene-butadiene polymers, butadiene-acrylonitrile polymers, carboxylated styrene-butadiene polymers, carboxylated butadieoe-acrylonitrile polymers, polymers comprising cbloroprene, polymers comprising acrylic monomers in latex form, and otber syntbetic rubbery polymers iD latex form such as butyl rubber, . .

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halogenated butyl rubber, polybutadiene and ethylene-propylene-ncn-conjugated diene polymers.
Preferred among tbese polymers are styrene-butadiene polymers in wbicb the average styrene content of toe polymer is from about 15 to about 40 per cent by weigbt, mixtures of two or more styrene-butadiene polymers in wbich tbe average s~yrene content is from about 45 to about 60 per cent by weigbt, carboxylated styrene-butadiene polymers in wbicb the styrene content is from about 15 to about 40 per cent by weigbt and the bound carboxylic acid monomer content is from about 2 to about 10 per cent by weigbt, butadiene-acrylonitrile polymers in wbich the acrylonitrile content is from about 20 to about 50 per cent by weigbt, carboxylated butadiene-acrylonitrile polymers in wbich the acrylonitrile content is from about 25 to about 40 per cent by weight and tbe bound carboxylic acid monomer content is from about 2 to about 10 per cent by weigbt and polymers comprising cbloroprene. Such preferred polymers may also contain compatible extender oil or plasticizer, suck as bydrocarbon oils for tbe styrene-butadiene polymers and alkyl esters for tbe butadiene-acrylonitrile polymers and polymers comprising chloroprene.
The fibrous material wbich may be used in this invention includes cellulose fibres such as cellulose, modified cellulose, cotton, jute, wood pulp and sisal, toe mineral fibres such as asbestos and mineral wool, syntbetic inorganic fibres sucb as glass fibres and glass yarn and syntbetic fibres such as rayon, nylon, polyester, polypropylene and aramid fibres. Preferred fibrous materials include fibres that are fibrilated especially sucb as to contain numerous fine diameter fibrils attacbed to the main fibre. An especially preferred fibrous material is tbe aramid fibre whicb is polymeric I:

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paraphenylene terepbt~alamide known as KEVLAR~ waving a surface area greater than l m2/g. The preferred KEVLAR
in tbe form known as wet pulp has a fibre lengtb of from about 1 to about 5 mm, preferably from about 2 to about

4 mm, has a BET surface area of from about 7 to about 12 m2/g and contains from about 40 to about 60 weigbt per cent of water. Examples of wet pulp have been described by duPont as merge #6F104 and #F2G5 and as having Canadian Standard Freeness, respectively, ox 450 to 575 and 300 to 425. Sucb fibrous material may be mixed with water and readily forms very trick suspensions of high viscosity even at concentrations of only about 2 weight per cent in water. If tbe fibrous material is dried to remove the residual water associated witb the wet pulp, it has been found tbat it is impossible to form a uniform mixture (using any of tbe conventional polymer mixing equipment) of tbe fibrous material witb any of tbe polymers described above under conditions regarded as practical by those skilled in tbe art. The fibres do not disperse evenly in the polymer and occur a9 agglomerations of fibre wltbin a polymer matrix.
The coagulants used in tbe process of this invention are tbose well known in toe art for the coagulation of the polymers from the latex. Suitable coagulants include tbe aqueous solutions of calcium cbloride, sulp~uric acid, sulpburic acid plus sodium cbloride, sulphuric acid plus sodium chloride plus a polyamine compound as exemplified in Canadian Patent 979,595, sulpburic acid plus polyamine compound, alum, alum plus sulpburic acid, polyaluminum chloride also known as aluminum polybydroxychloride, magnesium sulphate and Abe like. Selection ox a suitable coagulant for use to coagulate any particular polymer from toe latex is readily known to one of average skill in toe art. For example, to _ 7 --3~,~

coagulate a styrene-butadiene polymer from the latex, one may use sulpburic acid, sulphuric acid plus salt, sulpburic acid plus salt plus polyamine compound or polyaluminum cbloride, to coagulate a butadiene-acrylonitrile polymer from the latex, one may use calcium chloride or polyaluminum cbloride and to coagulate polymers comprising cbloroprene from tbe latex, one may use tbe polyvalent inorganic salts including calcium salts and alum.
Tbe process of tbe present invention requires tbat tbe polymer latex be added to an agitated aqueous solution of tbe coagulant whicb also contains fibrous material suspended in the coagulanc solution. Toe aqueous solution of the coagulant wbich also contains fibrous material suspended therein is prepared by adding tbe fibre to the coagulant solution, preferably to produce a dilute dispersion containing not more than about 1 weight per cent oE ibre in the coagulant solution, and to subject the dispersion of Eibre in coagulant solution to agitation for a short period ox time to improve the separation from one another of toe ibres before the polymer is added.
Such agitation may be accomplished by any known means especially such as to achieve preferably a high degree of sbearing action and would be for a period of time of from a few seconds, sucb as 2 or 3 seconds, up to not more tban about 30 to 40 seconds. Tbe polymer latex is then added to tbe dispersion of fibre in coagulant solution while the dispersion is being subjected to simple agitation. The fibrous material may be present in tbe coagulant solution 3~ as the total amount of fibre to be used or may be added as a dispersion in coagulant solution to the coagulation mixture continuously or intermittently as the latex is being added to the coagulant solution. Thus, for a batch type coagulation, it may be preferable to add all tbe .
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Tbe coagulation will generally be undertaken witb the coagulant solution maintained a a temperature of from about 25 to about 80C, preferably from about 40 to about 70C. The coagulant solution will be continuously agitated in order to mix all the components together. For a continuous process, coagulant solution will generally be continuously added to the coagulation mixture at a rate sufEicient to provide toe required coagulation action and toe co-coagulate~ polymer-fibrous material mixture will generally be removed continuously, sucb as by overflow from tbe vessel as a suspension in the aqueous phase of coagulated poLymer-fibre particles.
The concentration of fibrous material in the mixture of polymer and fibrous materiel is from about 0.25 to about 100 parts by weight of fibrous material per 100 parts by weight of polymer. In one preferred embodiment, the concentration of fibrous material is from about 0.25 to about 20, most preferably from about 2 to about 12, parts by weigbt per 100 parts by weight of polymer. In a second preferred embodiment, the concentration of fibrous material is from about 25 to about 100 parts by weigbt per 3~ 100 parts by weigbt of polymer. Tbe polymer latex will usually bave a polymer content ox from about 10 to about ~5 weigbt per cent of polymer based on the latex, ` preferably from about 15 to about 30 weight per cent of polymer. Tbe coagulant solution will contain the normal .

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concentrations ox coagulan~s, that is from about 0.5 up to about 8 weight per cent, and acid concentrations, wben used, will be such as to provide a pH of from about 2 to about 5. All flows of the various streams will be establisbed to provide the required relative concentrations of components. The fibrous material is mixed with and suspended in water, wig suspension is added to some or all of the aqueous coagulant solution.
Tbe concentration of fibrous material in the suspension in water is not important - it may range from about 0.1 up to about 5 per cent by weigbt provided what it is still a pumpable suspension. The concentration of fibrous material in the coagulant solution will generally be from about 0.1 to about 0.5 per cent by weight.
Tbe co-coagulation product, tbat is the mixture of polymer and fibrous material, i9 separated Erom the aqueous phase such as by mechanical separation means or by filtration, may be washed witb water, is recovered and tbe wet particLes of polymer-fibrous material mixture are dried, such as in a hot air drier or in a dewatering-drying means.
Tbe mixture of polymer and fibrous material may be used in many of the end-uses normal or the polymer itself - suck as various automotive products, tires, mechanical goods and the like as applicable for the particular type of polymer. For example, a KEVLAR wet pulp-styrene-butadiene mixture may be used in various aspects of tire construction including, but no limited to, in tbe apex (which is the area above tbe bead wire sometimes referred to as filler or bead filler), as a carcass protecting layer under the tread and sidewall, as a sidewall component to improve cut and snag resistance and in toe undertread (sometimes called the base) to provide improved cut resistance especially for on/off road ; _ 10 -,;

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use in agricultural and such tires. Toe mixture of polymer and fibrous material may also be used in mixtures wit one or more compatible polymers. Tbus, for example, the mixture of polymer and fibrous material may be mixed with polymers not containing fibre to produce a Einal mixture containing a lesser content of fibrous material per ooe hundred parts of total polymers. To illustrate, a mixture of styrene-butadiene polymer and fibrous material may be mixed wit a styrene-butadiene polymer containing no fibre and compounded in the usual manner, or a mixture of a polymer comprising chloroprene and fibrous material may be mixed witn a polymer comprising c~loroprene and containing no fibre and compounded in the usual manner, or a mixture of a butadiene-acrylonitrile polymer and fibrous material may be mixed with polyvinyl chloride containing no fibre and then compounded in the usuaL way, or a mixture of styrene-butadiene polymer and fibrous material may be mixed with one of or both of polybutadiene and natural rubber containing no fibre and compounded in tbe usual manner In all such uses, the polymer-fibrous material mixture will be compounded in the usual way wit rubber compounding ingredients, such as fillers, extenders or plasticizers, antloxidants or antiozonants and the like, and witb vulcanization active agents using rubber mills or internal mixers. The compounded mixtures will be shaped and tben vulcanized by maintaining at an elevated temperature for a period of time, such as by heating to about 140 to about 250C for times of from about 5 minutes to about 2 hours.
Vulcanizates containing toe polymer-fibrous material mixture of the invention possess improved properties when compared to vulcanizates of the same polymer cootaining no fibre. Suck improved properties may include one or more of improved dimensional stability, :.~

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increased modulus at low or moderate degrees of deformation and substantially increased resistance to tearing.
Tbe following Examples illustrate tbe scope of toe invention. All parts are parts by weigbt unless expressly shown otherwise. Tests used Jo evaluate the vulcanizate properties are ASTM tests adapted particularly for use witb small samples of material. Tbe fibrous material was used as provided and contained about 53 weight per cent of water.
Example l A styrene-butadiene polymer (about 24 weight per cent of styrene) in latex form (about 22 per cent solids) and an aramid fibre KEVLAR~ supplied as We Pulp having an average length of about 4 mm, merge number 6Fl04, Canadian Standard Freeness 450 to 575 and BET surface area of about lO m2tg and supplied as a solid material concaining about 53 per cent of water, were used. Tbe aramid fibre, as supplied, was added to water and subjected to vigorous agitation Eor about 5 minutes to provide a suspension oE
fibres in water with few, iE any, agglomerations of fibre.
In Experiment #1, tbe fibre was suspended in water, mixed witb the latex and tbe mixture maintained under agitation. A l per cent solution of calcium cbloride in water was slowly added to tbe mixture. This caused tbe formation of an agglomeration of at least part of tbe polymer and fibre which could not be adequately recovered. Tbis experiment was a control. In Experiment #2, tbe latex was diluted with water (no fibre was added) and tben added to a stirred 1% solution of calcium cbloride - tbis led to tbe formation of an agglomeration of at least part of tbe polymer wbic~ could not be adequately recovered. Tbis experiment was a control. In `Experiment #3, toe fibre was suspended in water and then 6~

mixed wit 120 ml of 1% calcium cbloride solution. Tbe latex was added to the stirred mixture of fibre and calcium cbloride wbicb led to toe formation of small particles of polymer and fibre wbicb was readily recovered, wasted with water and dried. Examination of tbe polymer-fibre mixture under a microscope showed it to be a uniform mixture of tbe components witbout significant agglomerations of fibre witbin the polymer. Tbe details are provided in Table I.
TABLE I
Experiment # 1 2 3 Weight of fibre g 2.8 - 2.8 Volume of water ml 200 300 300 Volume of latex ml 200 200 200 Volume of calcium ml cbloride solution - 120 120 Using tbe materials described in Example 1, a furtner batch co-coagula~ion was conducted similar to Experiment #3 thereof. 2.8 g of fibre was suspended in 300 ml of water wbic~ was tben mixed with 120 ml of 1%
calciùm chloride solution. 200 ml of latex was slowly added to the stirred mixture of fibre and calcium cbloride. Tbe nature of the coagulating mixture was observed during tbe course of toe latex addition and it was found tbat tbe polymer from tbe latex appeared to coagulate about tbe fibres, following wbicb tbe polymer appeared to coagulate onto the surface of the so-formed particles.
Example 3 Continuous co-coagulations were undertaken using tbe latex and fibre of Exampl l. A coagulation vessel ,, 3~,~

was provided and equipped wit an agitator and con-taining coagulant. A vessel was provided and eguipped witb an air-driven stirrer aod an outlet flow control means to dispense controlled amounts of the fibre-water suspension to toe coagulation vessel. A vessel equipped witb an ouclet flow control capable of providing a controlled flow of latex per unit time was used to supply latex to the coagulation vessel. For Experiments #4 and ~5, the coagulant was a mixture of 900 ml of a 4%
solution of sodium cbloride in water and 75 ml of a coagulant solution which contained 443 g of sodium chloride and 17.6 g of concentrated sulphuric acid in 3540 g of distilled water. For Experiment #6, the coagulant was a solution containing 0.25 weight per cent of calcium chloride dissolved in distilled water. Tbe fibre in water suspension contained for Experiment #4 1.4 g of fibre in 280 ml of water and was added in 9 ml aliquots over 13 minutes, for Experiment #5 1.4 g of fibre ln 280 ml oE water and was added in 9 ml aliquots over 6.5 minutes, and for Experiment #6 1.4 g of fibre in 280 ml of 0.2 weight per cent calcium chloride solution and was added in 9 ml aliquots over 13.5 minutes. For all the experiments, toe Eirst aliquot of fibre in water was added before the latex was added to the coagulation vessel. The latex was added to toe coagulation vessel over 14.5 minutes for Experiment #4, 7.15 minutes for Experiment #S
and 15 minutes for Experimenc #6. For Experiment #7, toe procedure of Experiment ~4 was followed except that 2.15 ml of a naphthenic oil (ASTM D 2226, Type 103) was also added at toe same time as the latex to the coagulation vessel over a cime for both oil and latex of ; 15.25 minutes.
All coagulations produced small crumbs of coagulated polymer and fibre which were readily separated .

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from tbe aqueous phase, washed and hot air dried to yield uniform mixtures containing essentially no agglomeracions of fibre.
Example 4 Following tbe procedure of Example 2, further co-coagulations were undertaken to provide samples of polymer containing varying amounts of fibre. The fibre was added to a 1% solution of calcium chloride in water and tbe latex was added thereto witb continuous agitation over a period of about 30 minutes. For toe Experiment #8, wbere no fibre was used, the coagulant was 2 g of calcium cnloride dissolved in 400 ml of water. The coagulated polymers were recovered and hot air dried, yielding uniform dispersions of fibre in polymer. Portions of the polymer-fibre mixture were compounded, shaped into streets, dumbbells cut for green strengtb measurements, the remaining sbeets were vulcanized at 160C for 10 minutes and dumbbells cut for vulcanizate property measurement.
Tbe compo~lnding recipe (based on 100 parts by weight of ~0 polymer) was 50 parts Oe carbon black, 3 parts of naphtbenic oil, 3 parts of zinc oxide, 1.5 parts of stearic acid, O.S parts ox N-(1,3-dimechylbutyl)-N'-phenyl-p-phenylene diamine, 0.5 parts Oe N,N'-bis(1,4-dimethylpentyl)-p-phenylene diamine, 0.3 parts Oe dipbenylguanidine, 1.2 parts of N-cert.butyl-2-benzothiazole sulphenamide and 2 parts of sulphur.
Further details are in Table II where eor the green strength and vulcanizate properties W means with the grain and A means against tbe grain. The iDcrease in green strength wittl increasing fibre content is readily seen.
The increase in 100% modulus and trouser tear for the vulcanizates is readily seen.
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, Example 5 Samples of polymer-fibre mixtures from Experiments #10-15 of Example 4 were mixed wit furtber polymer of tbe same type used in Experiment #8 to provide final mixtures all containing 3 parts of fibre per bundred parts of polymer. Tbis was done in duplicate using two different procedures. In tbe first procedure, tbe polymer-fibre mixture was banded on a two roll mill and tbe polymer slowly added, banded again, 3/4 cuts were made, 4 endwise passes were made and tbe product was finally sheeted off tbe mill. In tbe second procedure, tbe polymer-fibre mixture and tbe polymer were botb added to a two roll mill, banded, 3/4 cuts made, 4 endwise passes were made and tbe product was finally sbeeted off tbe mill.
Examination of tbe final products sbowed tbem all to be uniform mixtures containing a few small agglomera-tions of fibres.
Example 6 Latex samples of different polymers were co-coagulated with fibre. Tbe procedure used was tbat described in Example 3. For Experiment #16, tbe polymer was a butadiene-acrylonitrile polymer (about 34 weigbt per cent oE acrylonitrile) in tbe latex form (about 26~/o solids), 100 ml of wbich was added to cbe coagulation vessel at a uniform rate over 14.6 minutes. Tbe coagula-tion vessel contained 1 litre of 0.3 weigbt per cent solution in water of calcium cbloride and was initially at 62C, tbe temperature falling to 52C at tbe end of the co-coagulation. Tbe fibre (1.7 g) was suspended in ` 330 ml of water and was added in 10 ml portions over 13.5 minutes. Tbe product was a small particle size crumb, was separated from the aqueous pbase, washed and tben dried in a bot air drier. Experiment ~17 was a control, wberein .
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, tbe latex was similarly coagulated except tbat no fibre was added.' Tbe products of Experiments #16 and 17 were compounded (100 parts of polymer) with 50 parts of carbon black, 5 parts of di-octyl pbthalate, 3 parts of zinc oxide, 1 part of stearic acidl 1.75 parts of sulpbur, 1.5 parts of benzothiazyl disulpbide and 0. 5 parts of tetrametbyl thiuram disulpbide. Vulcanization was 4 minutes at 160C. For Experiment #18, the polymer was a styrene-butadiene polymer containing about 58 weight per cent of styrene in tbe latex form (about 27 . 3/o soLids), 100 ml of wbich was added to the coagulation vessel at a uniform rate over 14.6 minutes. Tbe coagulation vessel contained 900 ml of a 4% solution of sodium cbloride in water and 75 ml of the coagulant solution described in Example 3 and was at a temperature of about 55 to 50C~ Tbe fibre (1. 75 g)` was suspended in 350 ml of water and was added in 10 ml aliquots over 13 minutes.
The product was a small particle size crumb wbicb was separated from tbe aqueous phase, washed and cben dried.
Experiment #19 was a control, wberein the latex was similarly coagulated except tbat no fibre was added. Tbe products oE Experiments #18 and 19 were compounded (70 parts of pol.ymer) witb 30 parts of styrene-butadiene polymer (about 23.5% oE styrene), 30 parts of silica, 1 part of octylated dipbenylamine, 5 parts of zinc oxide, 2 parts of dietbylene glycol, 1 part of stearic acid, 1. 5 parts of benzotbiazyl disulpbide, 0.3 parts of tetrametbyl thiuram disulphide and 2.5 parts of sulpbur.
Vulcanization was for 10 minutes at 160C~ For Experiment #20, tbe polymer was a carboxylated butadiene acrylonitrile polymer containing about 29~/o of acrylonitrile and about 7% of carboxylic acid in tbe latex form (about 26~1% solids), 100 ml of wbich was added to the coagulation vessel at a uniform rate over 15 minutes.

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Tbe coagulation vessel contained 1000 ml of a 6% solution of sodium chloride, sufficient sulphuric acid was added to maintain tne pH at 2.5 and was at a temperature of about 50C. Tbe fibre (1.66 g) was suspended in 320 ml of water also containing 18 g oE sodium cnloride and was added in 10 ml aliquots over 14 minutes. Toe product was separated from tbe aqueous phase, washed wit water and then dried. Experiment #21 was a control, wberein the latex was similarly coagulated except that no fibre was added. Tbe products of Experiments #20 and 21 were compounded (95 parts of polymer) wit 50 parts of carbon black, l par of stearic acid, 1.5 parts of tetramethyl tbiuram disulpbide, 1.5 parts of sulpbur and 10 parts of a 50/50 masterbatch of ~utadiene-acrylonitrile polymër and zinc oxide. Vulcanization was for 9.5 minutes at 160C. Tbe results are shown in Table III.

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Example 7 A sample of a polyc~loroprene latex (Neoprene Latex 102) was co-coagulated wit fibre. 1.45 g of fibre was suspended witb agitation in an aqueous solution of 400 ml water, 4 g of alum, 20 g sodium cbloride and 75 ml of the coagulant solution described in Example 3, which was maintained at about 60C. 50 ml of toe latex (45.6%
solids) was slowly added to tbe agitated mixture resulting in the formation ox a stall particle size crumb of polymer plus fibre wbich was separated, wasbed wit water until tbe wasn waxer Tad a pH of about 7 and air dried. This was labeLled as Experiment #22. A control coagulation was also undertaken witb no fibre present as Experiment #23.
Tbe polymers were compounded (based on 100 parts of polymer) wit 40 parts of carbon black, 4 parts of magnesium oxide and 5 parts of zinc oxide. Vulcanization was Eor 20 minutes at 160C. The results are shown in Table IV.
TABLE IV
2 n Experiment 22 23 Fibre content oE 3 0 polymer-ibre mixture pbr Compound Green Strengtb Max. Stress (W) MPa 6.2 4.4 (A) MPa 5.9 Elongation (W) MPa 105 155 (A) MPa 145 Vulcanizate Properties 100% Modulus (W) MPa 16.4 15.9 (A) MPa 15.5 12.8 30Tensile Strengtb (W) MPa 19.0 21.3 (A) MPa 18.6 18.9 Elongation (W) % 120 125 (A) % 110 130 Tensile Set OW) % 0 0 (A) % 0 0 -Trouser Tear (W) kN/m 3.9 3.8 (A) kN/m 4.2 4.0 :

-Z36~

Example 8 A fibre dispersion was prepared by dissolving 7.5parts by weight of calcium cbloride in 1500 parts by weight of water aDd adding, with mild agitation, 10.4 parts by weight of tbe fibre of Example l. The dispersion was tben subjected to agitation for 20 seconds in a lab mixer. A sample of butadiene-acrylonitrile polymer latex (about 34 weigbt per cent of bound acryloni~rile) was prepared by adding lO0 parts by weigbt of water to 38.5 parts by weigbt of a latex wbich contained about 10 parts by weight of polymer. The latex was tben slowly added to tbe fibre dispersion with agitation. Tbe polymer coagulated and physically covered tbe fibre. The product was separated from tbe aqueous phase, wasbed and recovered and yielded a polymer-fibre mixture whicb contained about 104 parts of fibre per L00 parts of polymer.
A sample (l part by weight) of tbis polymer-fibre mixture was mixed on a rubber mill witb 10 parts by weight of a bucadiene-acrylonitrile polymer (about 34 weight per cent oE bound acrylonitrile) and afcer about :L5 minutes of mixing yielded a product containing an essentially uniform dispersion oE fibre in polymer (i.e. about 0.5 parts of fibre in about 10.5 parts of polymer), whicb sbows that the concentrated (in fibre) polymer-fibre mixture can be used to provide an essentially uniform mixture of a lesser proportion of tbe fibre in polymer.
Example 9 A fibre dispersion was prepared as in Example 8.
A sample of styrene-butadiene polymer latex (about 23 weigbt per cent of bound styrene) was prepared by addiog 100 parts by weigbt of water to about 46 parts by weigbC
of a latex wbicb contained about 10 parts by weigbt of polymer. Tbe latex was tben slowly added to tbe fibre dispersion with agitation and the coagulated polymer-fibre mixture was separated, wasbed and dried to yield a polymer-fibre mixture wbich contained about 104 parts of fibre per 100 parts of polymer.
Samples of the polymer-fibre mixture were mixed, separately, on a rubber mill or in a lab sized internal mixer with furtber styrene-butadiene polymer or with polybutadiene and produced, after adequate mixing time, essentially uniform dispersions of fibre in polymer.

. , .

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for the production of mixtures of polymer and fibrous material, said process comprising the steps of providing an agitated aqueous solution of coagulant for the polymer, adding an aqueous suspension of said fibrous material to the coagulant solution, adding said polymer in aqueous latex form to said coagulant solution and co-coagulating said polymer and fibrous material, and recovering and drying the mixture of polymer and fibrous material, said fibrous material being a polymeric paraphenylene terephthalamide aramid having an average length of from about 1 to about 5 mm and a BET
surface area of greater than 1 m2/g.

2. The process of Claim 1 wherein the fibrous material is the aramid fibre used in the wet pulp form and having a BET surface area of from about 7 to about 12 m2/g.

3. The process of Claim 2 wherein the polymer in aqueous latex form is selected from synthetic rubbery polymers produced by emulsion polymerization and from other synthetic rubbery polymers in latex form.

4. The process of Claim 3 wherein the polymer in aqueous latex form is selected from synthetic rubbery polymers produced by emulsion polymerization comprising styrene-butadiene polymers, butadiene-acrylonitrile polymers, carboxylated styrene-butadiene polymers, carboxylated butadiene-acrylonitrile polymers, polymers comprising chloroprene and polymers comprising acrylic monomers.

5. The process of Claim 3 wherein the polymer in aqueous latex form is selected from other synthetic rubbery polymers in latex form comprising butyl rubber, halogenated butyl rubber, polybutadiene and ethylene-propylene-non-conjugated diene polymers.

6. The process of Claims 1 or 2 wherein the amount of fibrous material in the mixture of polymer and fibrous material is from about 0.25 to about 20 parts by weight of fibrous material per 100 parts by weight of polymer.

7. The process of Claims 3, 4 or 5 wherein the amount of fibrous material is from about 2 to about 12 parts by weight of fibrous materials per 100 parts by weight of polymer.

8. The process of Claims 1 or 2 wherein the amount of fibrous material in the mixture of polymer and fibrous material is from about 0.25 to about 100 parts by weight of fibrous material per 100 parts by weight of polymer.

9. The process of Claims 3, 4 or 5 wherein the amount of fibrous material in the mixture of polymer and fibrous material is from about 25 to about 100 parts by weight of fibrous material per 100 parts by weight of polymer.

10. The process of Claims 1 or 2 wherein the aqueous latex contains from about 10 to about 45 weight percent of polymer based on the latex and the coagulation is undertaken with the coagulant solution maintained at a temperature of from about 25° to about 80°C.

11. The process of Claims 1 or 2 wherein the co-coagulation is a continuous process in which the suspension of fibrous material is added continuously or intermittently to the coagulant solution while the latex is being added provided that part of the suspension of fibrous material is present in the coagulant solution before the addition of latex is initiated.

12. The process of Claim 2 in which the polymer in aqueous latex form is selected from synthetic rubbery polymers produced by emulsion polymerization, the amount of fibrous material in the mixture of polymer and fibrous material is from about 0.25 to about 20 parts by weight per 100 parts by weight of polymer and the coagulation is undertaken with the coagulant solution maintained at a temperature of from about 25° to about 80°C.

13. The process of Claim 12 wherein the polymer is selected from a styrene-butadiene polymer, an acrylonitrile-butadiene polymer and a polymer comprising chloroprene.

14. Polymer-fibrous material mixtures produced by the process of Claim 1.

15. Polymer-fibrous material mixtures produced by the process of Claim 12.

16. Polymer-fibrous material mixtures produced by the process of Claim 13.

17. Vulcanizates produced by the steps comprising mixing a mixture of polymer and fibrous material with rubber compounding ingredients and vulcanizing the shaped mixture by heating at an elevated temperature, wherein said mixture of polymer and fibrous material is produced by the process comprising the steps of providing an agitated aqueous solution of coagulant for the polymer, adding an aqueous suspension of said fibrous material to the coagulant solution, adding said polymer in aqueous latex form to said coagulant solution and co-coagulating said polymer and fibrous material, and recovering and drying the mixture of polymer and fibrous material, said fibrous material being a polymeric paraphenylene terephthalamide aramid wet pulp having an average length of from about 1 to about 5 mm and a BET surface area of from about 7 to about 12 m2/g.

18. The vulcanizate of Claim 17 wherein the polymer in aqueous latex form is selected from synthetic rubbery polymers produced by emulsion polymerization, the amount of fibrous material in the mixture of polymer and fibrous material is from about 0.25 to about 20 parts by weight per 100 parts by weight of polymer and the rubber compounding ingredients include any one or more of filler, extender or plasticizer, antioxidant and antiozonant.

19. The vulcanizate of Claim 17 wherein the polymer in aqueous latex form is selected from synthetic rubbery polymers produced by emulsion polymerization, the amount of fibrous material in the mixture of polymer and fibrous material is from about 25 to about 100 parts by weight per 100 parts by weight of polymer and the rubber compounding ingredients include any one or more of filler, extender or plasticizer, antioxidant and antiozonant.

20, The vulcanizate of Claims 17, 18 or 19 in which the polymer is selected from a styrene-butadiene polymer, an acrylonitrile-butadiene polymer and a polymer comprising chloroprene.

21. The vulcanizate of Claims 17, 18 or 19 wherein the shaped mixture is vulcanized by heating at a temperature of from about 140° to about 250°C for a time of from about 5 to about 120 minutes.

22. The vulcanizate of Claims 17, 18 or 19 wherein the mixture of polymer and fibrous material is mixed with one or more compatible polymers.