GB1601434A - Vulcanisates containing siliceous fillers - Google Patents

Description

(54) VULCANIZATES CONTAINING SILICEOUS FILLERS (71) We, POLYSAR LIMITED. a company organised under the laws of Canada, of Sarnia, Ontario, Canada, do hereby declare the invention, for which we pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement: This invention is directed to improved silica-filled or calcium silicate-filled rubbery vulcanizates. In particular, the polymer of the filled vulcanizate contains certain selected groups which are caused to interact with the silica or calcium silicate.

The effects due to the presence of fillers in polymer vulcanizates are well known.

Comparison of a gum vulcanizate with a filled vulcanizate shows the improved strength and wear characteristics in the filled vulcanizate when the filler used belongs to the class known as reinforcing fillers. The types of fillers that may be compounded with polymers are quite diverse in nature, the selection of the type of filler being mainly dependent on the properties required of the vulcanizate denved therefrom, but are normally divided into reinforcing and non-reinforcing types. From the group of reinforcing fillers, two which have received the most attention are the various carbon blacks and silicas. Of these two types, carbon black is the most dominant because of price and the overall balance of vulcanizate properties.

There has existed a desire to improve the characteristics of silica-filled and silicate-filled vulcanizates and to make them more closely equivalent to carbon black filled vulcanizates.

This desire arises partly from the fact that light colored vulcanizates, which obviously cannot contain carbon black, have a definite place in the market and partly from the fact that silica and silicates do not depend, in principle, upon the use of hydrocarbons for their manufacture. Any attempt to improve the properties of silica or silicate filled vulcanizates to more closely match the properties of carbon black filled vulcanizates is thus timely and would fill a need long recognized by the industry.

Vulcanizates obtained from silica or silicate filled polymers, while having certain useful properties, are known to be deficient due to being boardy, which may be described as a stiffness at low elongations and lack of resilience, and due to high tensile set, both of which deficiencies can be avoided in carbon black filled vulcanizates.

In attempts to overcome some of the deficiencies associated with the use of silica fillers in polymers, silica has been treated with a number of chemicals to modify the chemical nature of the surface of the silica particles. Thus silica has been treated with diazomethane, with alcohols, and with a range of organo-silanes including, for example, trimethylchlorosilane.

However, these treatments, while leading to minor improvements, were not successful in overcoming the overall deficiencies.

Other chemical compounds have been mixed with silica-polymer systems for a different reason. Silica, due to its highly absorbtive surface, tends to preferentially absorb the chemical curing agents normally used which leads to undercuring during the vulcanization step. In order to overcome this problem certain chemicals such as glycols, e.g. diethylene glycol or poly(ethylene glycol), amines, e.g. triethanolamine and guanidines have been added during the compounding steps and allow the use of normal levels of curing agents to achieve the expected level of cure. The overall aforementioned deficiencies are still found in such vulcanizates.

None of these chemical treatments or chemical additives have overcome the deficiencies associated with the use of silica as filler in polymeric vulcanizates.

A more recent improvement in the art of using silica as a filler for polymers is the use of coupling agents. Significant improvements in the vulcanizate properties can be attained when coupling agents are added. The most effective coupling agents are organofunctional silanes; titanium-containing compounds are also known. Suitable organofunctional silanes include the mercaptosilanes. Vulcanizates containing mercaptosilanes added to the silica filler during the compounding stage generally show, in comparison with silica-filled vulcanizates not containing such silanes, increased values for modulus and tensile strength, and decreased elongation at break - generally, properties more comparable to the properties of carbon black filled vulcanizates. Although a number of coupling agents are commercially available, their cost is extremely high, making them not very practical for general use.

Thus, the problem still exists that silica-filled vulcanizates, of reasonable cost, cannot be produced to have acceptable strength, resilience and tensile set properties.

The present invention concerns a process for the production of a filled rubbery vulcanizate comprises shear mixing at a temperature of 100 to 175"C a mixture of 100 parts by weight of a vulcanizable polymer containing, per 100 grams thereof, from 1.5 to 80 millimoles of hydroxyl groups, from 5 to 100 parts by weight of filler selected from silica and calcium silicate, and an additive, cooling the mixture, incorporating into the mixture vulcanization active compound and vulcanizing by heating.

According to a first aspect of the present invention, the additive comprises from 0.5 to 5 parts by weight, per 100 parts by weight of polymer, of an amine selected from compounds of the formulae R-NH2, R-NHR' and R-NR"R"' wherein R is C4 30 alkyl or alkenyl which may contain up to three NH2, NH or NR" groups, C4) cycloalkyl or C7 20 aralkyl, R' is C4 30 alkyl or alkenyl and R" and R" are the same or different Cl l0 alkyl.

According to a second aspect of the present invention, the additive comprises from 1 to 5 parts by weight, per 100 parts by weight of polymer, of an acid selected from C15.20 saturated or unsaturated fatty acids, aromatic carboxylic acids and aryl sulphonic acids, and the alkali metal, alkaline earth metal, zinc and ammonium salts of the fatty or carboxylic acids.

According to a third aspect of the present invention, the additive comprises from 1 to 10 parts by weight, per 100 parts by weight of polymer, of magnesium oxide.

In order to establish whether improved vulcanizate properties are achieved, it is necessary to be able to define these properties in measurable quantities. For vulcanizates of polymeric materials, the conventional type of stress-strain measurement supplies much useful information. Prior art silica-filled vulcanizates exhibit, in comparison with carbon black filled vulcanizates, a higher modulus at low degrees of extension (e.g. 25% strain) and a lower modulus at high degrees of extension (e.g. 300% strain). By means of slow rate extension tests, the modulus at 25% extension is readily determined. Further, the slope of the stress-strain curve at zero extension can also be determined; this is the Young's modulus. The Young's modulus and the 25% modulus illustrate the stiffness at low elongations.Stress-strain tests conducted at the conventional rates of extension provide the 100% modulus, the 300who modulus, the elongation at break and the tensile strength. On completion of a stress-strain test, the two ruptured pieces of the test specimen are, ten minutes after rupture, carefully fitted together so that they are in contact over the full area of the break - the distance between the two bench marks is measured. The tensile set is the extension remaining in the test piece and is expressed as a percentage of the original test piece length. Thus, test procedures are known whereby it is readily possible to quantify the quality of the vulcanizates.

The polymers which are used in the present invention are vulcanizable polymers which contain functional groups attached to the polymer chain. The functional groups are hydroxyl and may be attached either directly to the polymer chain or may be attached to the polymer chain through a hydrocarbyl group. Suitable vulcanizable polymers are essentially C4-C6 conjugated diolefin polymers, copolymers of C4-C6 conjugated diolefins and at least one other copolymerizable vinyl or vinylidene-containing monomer, polymers comprising a C4-C6 isoolefin and polymers comprising one or two alpha olefins.Examples of such suitable polymers include polybutadiene, polyisoprene, butadiene-styrene polymers, isoprene-styrene polymers, butadiene-acrylonitrile polymers, butadiene-methacrylonitrile polymers, isoprene-acrylonitrile polymers, isobutylene-isoprene polymers, ethylenepropylene polymers and ethylene-propylene-non-conjugated diolefin polymers. All the polymers are solid high molecular weight materials, having Mooney viscosities within the range of about (ML 1 + 4 at 100"C) 30 to about 150. The functional groups may be incorporated into the polymers by copolymerization of suitable monomers or by chemical modification of the polymer.Incorporation of the functional groups by copolymerization can only be achieved in an emulsion free radical polymerization system whereas incorporation of the functional groups by chemical modification can be achieved with polymers prepared by emulsion free radical polymerization and with polymers prepared by other methods of polymerization. One of average skill in the art will be able to readily relate monomers suitable for emulsion free radical polymerization. Suitable copolymerizable monomers include hydroxethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate or methacrylate, hydroxypropyl crotonate, di(2-hydroxyethyl) maleate, di(2hydroxyethyl) fumarate, N-ethanol acrylamide, hydroxyethyl vinyl ether and diethyleneglycol monovinyl ether.Suitable chemical modification may include partial epoxidation followed by reduction of carbon-carbon double bonds in a polymer containing unsaturation, treatment with an alkali metal alkyl compound such as butyl lithium followed by hydrolysis and hydrolysis of halogen groups in a polymer molecule. Thus the polymers which may be used in this invention are the vulcanizable polymers hereinbefore described and containing hydroxyl groups attached to the polymer chain.

The concentration of the bound functional groups in the polymer is 1.5 to 80 millimoles per 100 grams of polymer. Preferably, the concentration of the bound functional groups is from 2 to 60 millimoles per 100 grams of polymer. Suitable concentration of the functional groups can also be achieved by mixing a polymer having a concentration of bound functional groups of from 20 to 80 millimoles per 100 grams of polymer with a like polymer having no functional groups, the two polymers being mixed in such a ratio that the concentration in the mixture of functional groups is from 4 to 60 millimoles of functional groups per 100 grams of the mixture of polymers.

The silica which is mixed with the polymer to produce the compounds and vulcanizates of this invention is of fine particle size, that is to say, generally less than 0.1 micron but larger than 0.01 microns average particle size. Such silicas are well known in the art and may be selected from the fumed silicas, which are relatively anhydrous, and from the precipitated silicas, which contain water of hydration. The calcium silicate is a precipitated calcium silicate containing water of hydration and having an average particle size of less than 0.1 micron but greater than 0.01 micron. Preferably, the silica has an average particle size of 0.015 to 0.05 microns and is a precipitated silica. Preferably, the calcium silicate has an average particle size of 0.015 to 0.05 microns.

The amount of silica or calcium silicate which may be mixed with the polymer is from 5 parts to 100 parts by weight per 100 parts by weight of polymer. In normal practice, the higher concentration of silica or silicate, that is, from 60 to 100 parts by weight per 100 parts by weight of polymer, will be mixed with polymers which may contain hydrocarbon oil or plasticizer or to which hydrocarbon oil or hydrocarbyl plasticizer is added during the compounding stage. Additional fillers may also be added to the silica-polymer mixture, such additional fillers being selected from the generally non-reinforcing or semi-reinforcing fillers such as calcium carbonate, titanium dioxide, calcium sulphate, clays and silicates and from the carbon blacks. Such additional fillers may be present in amounts from 5 to 150, preferably from 5 to 80, parts by weight per 100 parts by weight of polymer.Carbon black may also be present at up to 3 parts by weight per 100 parts by weight of polymer as a coloring agent.

The additive which is added to the silica or calcium silicate polymer mixture is a material which appears to promote a reaction between the functional groups of the polymer and the silica or silicate surface. The exact nature of the role played by this additive is uncertain at this time but it is known that the presence of such a material in the silica or calcium silicate polymer mixture during the heating and shearing action leads to improved properties of the vulcanizates.

Typical examples of suitable amine additives include hexylamine, decylamine, octadecylamine, 1,1 -dimethyldecylamine, 1, 1-diethyloctadecylamine, octadecenyl amine, N,Ndimethyldecylamine, N,N-diethyloctadecylamine, di-(dodecyl)amine, hexamethylenediamine, triethylenetetramine and N,N,N' ,N'-tetramethylhexamethylenediamine.

Preferred amines include the compounds of formula R-NH2 and R-NHR', wherein R is a C10-C20 linear or branched alkyl or alkenyl group which may contain 1 NH2 or NH group and R' is a C10-C20 linear or branched alkyl or alkenyl group. Most preferred amines are compounds of formula R-NH2 wherein R is a C10-C20 linear or branched alkyl or alkenyl group.

The quantity of the amine additive added to the silica or calcium silicate polymer mixture is from 0.5 to 5 parts by weight of additive per 100 parts by weight of polymer. Preferably the quantity of the additive added is from 1 to 3 parts by weight of additive per 100 parts by weight of polymer. The additive may be added to the silica or calcium silicate polymer mixture either during the initial mixing of the silica or silicate and polymer, it may be added in a subsequent mixing operation or it may have been added previously to the silica or silicate.

The additive may also be selected from organic acids and salts thereof. Suitable C15-C20 fatty acids include palmitic acid and stearic acid; suitable C15-C20 unsaturated fatty acids include oleic acid and linoleic acid; suitable aromatic carboxylic acids include benzoic acid, phthalic acid, cinnamic acid and hydroxybenzoic acid; suitable salts of these acids include the sodium, potassium, calcium, zinc and ammonium salts. Suitable aryl sulphonic acids include benzenesulphonic acid, the toluenesulphonic acids and the xylenesulphonic acids.

Preferred organic acids or salts thereof are stearic acid and the sodium, potassium, or zinc salts thereof.

The quantity of the acid or salt additive added to the silica or calcium silicate polymer mixture is from 1 to 5 parts by weight of chemical per 100 parts by weight of polymer.

Preferably the quantity of the additive added is from 1 to 3 parts by weight of additive per 100 parts by weight of polymer. The additive may be added to the silica or calcium silicate polymer mixture either during the initial mixing of the silica or silicate and polymer or it may be added in a subsequent mixing operation.

The additive may also be magnesium oxide, the quantity added to the silica-polymer mixture being from 1 to 10 parts by weight of chemical per 100 parts by weight of polymer.

Preferably the quantity of magnesium oxide added is from 5 to 10 parts by weight of additive per 100 parts by weight of polymer. The additive may be added to the silica-polymer mixture either during the initial mixing of the silica and polymer or it may be added in a subsequent mixing operation.

It is necessary that the silica or calcium silicate polymer mixture be subjected to a treatment wherein it is sheared at an elevated temperature in the presence of the additive.

Such shearing may be achieved on a two-roll rubber mill or in an internal mixer and may be during the mixing of the polymer and filler or as a subsequent step to such mixing. The elevated temperature is from 100" to 1750C, preferably from 1200 to 1600C. The mixture is subjected to such treatment for from 0.25 to 10 minutes, preferably from 0.5 to 5 minutes.

For ease of operation, it is preferred to add the additive during the initial mixing of the silica or silicate and polymer.

The mixing of the silica or calcium silicate and polymer may be achieved using conventional rubber mixing equipment including two roll rubber mills and internal mixers.

The subsequent addition, after cooling from the shearing at elevated temperature, of other compounding ingredients and vulcanization active compounds is by means conventional in the rubber industry including, especially when vulcanization active compounds are involved, two roll rubber mills operated at relatively low temperatures, usually below 65"C.

Suitable vulcanization systems are chosen to match the nature of the polymer and the intended use for the vulcanizate and are well known in the industry. The nature of the vulcanization system is not critical to this invention. The compounds are vulcanized by heating at an elevated temperature, for example at temperatures of 125 - 200"C for times of from 1 minute to 10 hours, preferably at temperatures of 150-170"C for from 3 to 60 minutes.

The vulcanizates produced from the silica or calcium silicate polymer mixtures of this invention possess significantly improved physical properties when compared with comparable prior art vulcanizates except those containing an organofunctional coupling agent.

Comparison of the vulcanizates of this invention when they contain 50 parts by weight of silica per 100 parts by weight of polymer with prior art vulcanizates also containing 50 parts of silica, shows that the vulcanizates of the present invention have at least one of and preferably at least two of the following properties: a reduced Young's modulus, a reduced modulus at 25% extension, an increased modulus at 300% extension, an increased tensile strength and a reduction in the tensile set. Preferably, the vulcanizates of this invention will have a reduced Young's modulus and a reduced 25% modulus and most preferably the vulcanizates will have a reduced Young's modulus, a reduced 25% modulus, an increased 300% modulus and a reduced tensile set.

The following examples are provided to illustrate, but not limit, the invention and all parts are parts by weight unless otherwise stated. "Hisil", "Silene", "DiCup", "Brabender", "Banbury", "Duomeen" and "Armeen" are believed to be registered Trade Marks.

Example I A polymer of butadiene, acrylonitrile and hydroxyethyl methacrylate was prepared, by conventional emulsion polymerization techniques at a temperature of 13"C. The polymer contained about 34 weight per cent of acrylonitrile and about 1 weight per cent of hydroxyethyl methacrylate.

A butadiene-acrylonitrile polymer containing about 34 weight per cent of acrylonitrile was prepared by an identical procedure for use as a control polymer.

Samples of these polymers (100 parts by weight) were mixed on a rubber mill, Experiments 1A and 2A, with 50 parts by weight of silica (HiSil 233) and 1.5 parts by weight of dodecylamine following which they were milled for three minutes with the mill rolls maintained at 1500C or with 60 parts by weight of calcium silicate (Silene EF), Experiment 1B, and 1.5 parts by weight of Armeen T and milled for 3 minutes at 1500C, Experiment 2B.

The compounded polymer was removed and cooled. When cold, the compounded polymer was returned to a rubber mill at room temperature and dicumyl peroxide (DiCup 40C in the amount shown in Table I) was added and thoroughly mixed in. The compounded polymer was sheeted off, put into a mold and vulcanized in a press at 1600C for 30 minutes.

Specimens were cut from the vulanizates so produced and tested. The results are given in Table I. The data clearly show that the vulcanizates of this invention exhibit significantly improved properties, including an improved tensile strength and 300% modulus, and a reduced Young's modulus and tensile set.

TABLE I Experiment No. 1 2 Polymer Butadiene-acrylo- Butadiene-acrylo nitrile nitrile-hydroxy ethyl methacrylate (Control) A B A B Wt. % HEMA in polymer 0 0 1 1 Wt. % dicumyl peroxide (based on polymer) 3.5 4.0 3.0 4.0 Vulcanizate properties Tensile strength kg/cm2 266 141 318 173 Elongation % 520 440 550 370 100% Modulus kg/cm2 27 32 26 33 300% Modulus kg/cm2 98 81 135 140 25% Modulus kg/cm2 10 12 5 10 Young's Modulus kg/cm 159 139 51 60 Tensile set % 15 10 10 5 Hardness Shore A2 80 76 70 70 Example 2 Polymers of butadiene, acrylonitrile and hydroxyethyl methacrylate were prepared as in Example 1 except that the quantities of butadiene and hydroxyethyl methacrylate (HEMA) were adjusted so that the total was always about 66 weight per cent of the polymer and the quantity of bound HEMA was varied from 0.25 to 5 weight per cent of the polymer. The amount of bound HEMA is shown in Table II. The additive was 1.5 parts by weight per 100 parts by weight of polymer, of dodecylamine. The compounding and hot milling procedures of Example 1 were followed, the compounded polymers were vulcanized by heating at 1600C for 30 minutes and the vulcanizates tested.

The results are given in Table II and show that the vulcanizates exhibit improved properties even when the HEMA level is as low as 0.25 weight per cent of the polymer.

TABLE II Experiment No. 10 11 12 13 14 15 Wt. % HEMA in polymer 0.25 0.5 1.0 1.5 2.0 5.0 Wt. % dicumyl peroxide (based on polymer) 1.5 2.0 2.0 2.5 1.5 1.0 Vulcanizate properties Tensile strength kg/cm 242 299 320 283 31S 235 Elongation Ck 360 410 380 420 410 390 100% Modulus kgicm 75 35 49 35 30 26 3005S Modulus kg/cm 196 199 239 181 209 160 25% Modulus kg/cm2 10 9 9 9 7 5 Young's Modulus kg/cm 73 63 51 57 42 29 Tensile set % 5 5 5 6 6 5 Hardness Shore A2 84 77 75 77 77 76 Example 3 Using a polymer of similar composition to that of Example 1, Experiment No. 2, containing 1 weight per cent of hydroxyethyl methacrylate, the effect was studied of a variety of amines, in place of the octadecylamine of Experiment No. 2A of Example 1. The specific amines were all added in an amount of 1.5 parts by weight per 100 parts by weight of the polymer. The dicumyl peroxide used was DiCup 40C. The hot milling was 3 minutes at 1500C. Vulcanization was for 30 minutes at 1600C.

The results are shown in Table III from which it is clear that primary, secondary and tertiary amines are effective additives in the process of this invention.

TABLE III Experiment No. 20 21 22 23 24 25 26 Amine Type Hexadecyl Ocadecyl N,N-Dimethyl Armeen T Di(dodecyl) Duomeen 5 Hexaamine amine octadecyl (C18H35NH2) amine RNH methylene amine diaminhe (CH2)2.NH2 Wt. % of dicumyl peroxide (based on polymer) 4.0 4.0 4.0 4.0 3.5 3.5 3.5 Vulcanizate properties Tensile strength kg/cm2 260 250 260 261 324 298 285 Elongation % 430 400 470 400 510 440 440 100% Modulus kg/cm2 30 30 28 30 26 28 33 300% Modulus kg/cm2 167 163 131 161 155 179 179 25% Modulus kg/cm2 9 9 9 7 8 8 10 Young's Modulus kg/cm2 56 61 79 46 49 51 72 Tensile set % 5 5 8 4 7 5 10 Hardness Shore A2 79 79 79 75 76 76 77 TABLE III (continued) Experiment No. 27 28 29 Amine Type Tri-octyl Tri-isooctyl Benzyl amine amine amine Wt. No of dicumyl peroxide 4.0 4.0 4.0 Valanizate properties Tensile strength kg/cm2 246 270 283 Elongation % 360 410 440 100% Modulus kg/cm2 35 35 30 300% Modulus kg/cm2 180 188 180 25% Modulus kg/cm2 9 9 9 Young's Modulus kg/cm2 65 67 53 Tensile set % 3 3 3 Hardness Shore A2 80 80 77 Example 4 A polymer of similar composition to that of Example 1 and containing 1 weight per cent of hydroxyethyl methacrylate was compounded, subjected to heat treatment, vulcanized and the vulcanizate properties were determined, as in Example 1, the difference being that the conditions of temperature and time for the heat treatment were varied as shown in Table IV.The amine used was dodecylamine the quantity being 1.5 weight per cent based on polymer and the amount of dicumyl peroxide was 3.5 weight per cent based on polymer, DiCup 40C being used. For Experiment No. 35, 100 parts of the polymer was mixed in a Brabender Plasticorder equipped with a Banbury mixing head with 50 parts of silica, 10 parts of dioctyl phthalate and 1.5 parts of Armeen T. The mixer was initially at a temperature of about 90"C and the mixing was continued for 8 minutes without control of the temperature which had risen to 139"C at the end of the 8 minutes. After cooling, the mixture was compounded on a cold mill with 4 parts of DiCup 40C and vulcanized.

The results shown in Table IV clearly demonstrate the need for heating under shearing conditions in order to obtain the improved vulcanizate properties.

TABLE IV Experiment No. 30 31 32 33 34 35 Temperature of heat treatment* "C 30 100 125 150 150 90-139 approx.

Time of heat treatment min. Nil 3 3 1 3 Vulcanizate properties Tensile strength 272 291 267 260 275 239 kg/cm2 Elongation % 620 520 520 510 530 670 100% Modulus kg/cm2 24 26 26 26 26 19 300% Modulus kg/cm2 70 90 110 109 108 70 25% Modulus kg/cm2 11 9 8 8 7 8 Young's Modulus 188 96 55 68 45 76 kg/cm2 188 96 55 68 45 76 Tensile set % 15 10 7 7 9 14 Hardness Shore A2 80 75 73 74 74 74 *Heat treatment - static, in a press Example 5 A polymer containing 1 weight per cent of hydroxyethyl methacrylate and similar to that of Example 1 was compounded with a fumed silica instead of the hydrated silica of Example 1. All other conditions were the same as for Example 1, the level of dicumyl peroxide being 4 weight per cent based on polymer.A control experiment was also made in which no dodecylamine was added prior to the heat treating step.

The vulcanizate properties are shown in Table V, from which it is clear that improved vulcanizate properties are achieved when using fumed silica.

TABLE V Experiment No. 40 41 (Control, no amine) Tensile strength kg/cm2 320 342 Elongation % 330 490 100% Modulus kg/cm2 36 30 300% Modulus kg/cm2 271 141 25% Modulus kg/cm2 20 12 Young's Modulus kg/cm2 274 110 Tensile set % 6 9 Hardness Shore A2 87 81 Example 6 Using a polymer of similar composition to that of Example 1, Experiment No. 2, and containing 1 weight per cent of hydroxyethyl methacrylate, the effect was studied of varying the level of Armeen T , expressed as weight per cent based on polymer, present during the heat treatment step. The silica was 50 parts by weight per 100 parts by weight of polymer.

For Experiment No. 56, the polymer contained 1 weight per cent of hydroxyethyl acrylate instead of hydroxyethyl methacrylate and for Experiment No. 57 for polymer contained about 1 weight per cent of 2-hydroxypropyl methacrylate. The quantity of DiCup 40C added was 4 weight per cent based on polymer, except 1.5 weight per cent for No. 57 and vulcanization was for 30 minutes at 1600C. For the control experiment. Experiment No. 50, no amine was present during the heat treatment step.

The results shown in Table VI clearly demonstrate that even 0.5 weight per cent of Armeen T leads to a significant improvement in the vulcanizate properties.

TABLE VI Exp. No. 50 51 52 53 54 55 56 57 Quantity of Armeen T 0 0.5 1.0 1.5 2.0 3.0 1.5 1.5 Vulcanizate properties Tensile strength kg/cm2 297 344 325 323 321 301 282 231 Elongation 440 380 350 330 370 370 340 430 100% Modulus kg/cm2 33 44 34 43 35 30 33 33 300% Modulus kg/cm2 171 255 270 280 250 230 223 145 25% Modulus kg/cm2 10 9 8 9 8 8 9 9 Young's Modulus kg/cm2 104 62 52 61 56 52 66 61 Tensile set % 6 6 2 4 4 4 4 5 Hardness Shore A2 79 74 73 73 71 71 74 76 Example 7 Using a conventional emulsion free radical polymerization procedure, a polymer was prepared which contained about 34 weight per cent of acrylonitrile, about 61 weight per cent of butadiene and 5 weight per cent of hydroxyethyl methacrylate.A commercially available acrylonitrile-butadiene polymer containing 34 weight per cent of acrylonitrile and having a Mooney (ML 1 + 4 at 100"C) of 50 was also used. Blends were prepared of the acrylonitrile-butadiene polymer and the acrylonitrile-butadiene-hydroxyethyl methacrylate polymer in the ratios shown in Table VII, and the blended polymers were mixed with 50 parts by weight per 100 parts by weight of polymer of silica and 1.5 parts by weight per 100 parts by weight of polymer of dodecylamine and heat treated at 1500C for 3 minutes, as in Example 1. Dicumyl peroxide (DiCup 40C) was added to the compounds which were vulcanized by heating at 1600C for 30 minutes.

The properties of the vulcanizates are shown in Table VII from which it is clear that blends containing as little as the equivalent of 0.25 weight per cent of hydroxyethyl methacrylate exhibit improved properties, and blends containing from the equivalent of 0.5 weight per cent of hydroxyethyl methacrylate exhibit much improved properties.

TABLE VII Experiment No. 60 61 62 63 64 65 Acrylonitrile-buta diene polymer - wt. 100 95 90 80 60 0 Acrylonitrile-buta diene hydroxyethyl methacrylate polymer weight 0 5 10 20 40 100 Equivalent HEM: content in blend - weight 0 0.25 0.5 1 2 5 Dicumyl peroxide wt. % based on polymer 5.0 4.0 4.0 4.0 3.5 1.0 Vulcanizate properties Tensile strength kg/cm2 225 235 242 275 255 235 Elongation % 400 440 370 390 300 390 100% Modulus kg/cm2 35 29 35 35 28 26 300% Modulus 136 123 171 189 255 160 kg/cm2 136 123 171 189 255 160 25% Modulus kg/cm2 12 12 11 10 9 5 Young's Modulus kg/cm2 184 172 96 72 46 29 Tensile set % 10 10 6 5 3 5 Hardness Shore A2 80 78 80 80 76 76 Example 8 The effect was studied of a sulphur cure, in place of a peroxide cure, on silica-reinforced polymers.As a control, a commercially available butadiene-acrylonitrile polymer was used which contained 34 weight per cent of acrylonitrile and had a Mooney (ML + 4 at 100"C) of 50. A butadiene-acrylonitrile-hydroxyethyl methacrylate polymer and containing 1 weight per cent of hydroxy-ethyl methacrylate was used to illustrate the present invention. The amine added was Armeen T, 1.5 weight per cent based on the polymer, and the heat treatment was on a rubber mill at 1500C for 3 minutes. Following the heat treatment, the compound was allowed to cool to ambient temperature and the remaining ingredients were added on a mill maintained at 35-40"C. The vulcanizate properties are shown in Table VIII, from which it can be seen that the vulcanizates according to this invention show significantly improved properties.The Table also shows that the scorch time can be affected by the incorporation of known scorch retarders (salicylic acid), as for Example Experiment No.

72.

TABLE VIII Experiment No. 70 71 72 Butadiene-acrylonitrile polymer - weight 100 Butadiene-acrylonitrile-hydroxy ethyl methacrylate polymer - 100 100 - weight Silica - weight 60 60 60 Di-octyl phthalate - weight 12.5 12.5 12.5 Armeen T - weight 1.5 1.5 1.5 Mill at 1500C for 3 minutes Zinc oxide - weight 5 5 5 Stearic acid - weight 1.5 1.5 1.5 Benzothiazyl disulphide - weight 1.5 1.5 1.5 Tetramethyl thiuram disulphide - weight 0.5 0.5 0.5 Spider Brand Sulphur - weight 1.75 1.75 1.75 Salicylic acid - weight - - 1.0 Scorch time (t5 at 1250C) min. - 6.5 20 Cure at 166"C for min. 5 15 15 Vulcanizate Properties Tensile Strength kg/cm2 250 273 273 Elongation % 700 580 560 100% Modulus kg/cm2 14 15 17 300% Modulus kg/cm2 50 89 98 25% Modulus kg/cm2 9 7 7 Young's Modulus kg/cm2 118 65 76 Tensile set % 26 13 13 Hardness Shore A2 78 75 75 Example 9 A styrene-butadiene-hydroxyethyl methacrylate polymer containing approximately 0.5 weight per cent of hydroxyethyl methacrylate and 23 weight per cent of styrene was mixed with 50 weight per cent of silica and 1.5 weight per cent of Armeen T and hot milled at 1500C for 3 minutes, as in Example 1. One control experiment was run in which no Armeen T was present. A second control experiment was run in which no amine was present and the hot milling was omitted.

The compounds so prepared were mixed at room temperature with the quantity of DiCup 40C shown in Table IX and then vulcanized for 30 minutes at 1600C.

The physical properties of the vulcanizates are shown in Table IX from which it is clear that the vulcanizate prepared according to the present invention has improved properties.

TABLE IX Experiment No. 80 81 82 Hot mill Yes Yes No Amine present Yes No No Dicumyl peroxide - wt. % based on polymer 1.0 0.67 0.67 Vulcanizate properties Tensile strength kg/cm2 245 191 240 Elongation % 500 530 540 100% Modulus kglcm2 24 15 28 300% Modulus kg/cm2 128 80 123 25% modulus kg/cm2 7 7 10 Young's Modulus kg/cm2 64 91 110 Tensile set % 5 9 14 Hardness Shore A2 75 72 79 Example 10 Using the polymer of Example 1 containing about 34 weight per cent of acrylonitrile and about 1 weight per cent of hydroxyethyl methacrylate, portions (100 parts by weight) of this polymer were mixed, on a rubber mill, with 50 parts by weight of silica (Experiment A) and for Experiment B additionally with 2 parts by weight of sodium stearate and for Experiment C additionally with 2 parts by weight of ammonium salicylate. The silica used was HiSil 233.

The compounds were heat treated on a rubber mill for 3 minutes at 1500C. After cooling, the compounds were put into a cool (about 40"C) rubber mill and dicumyl peroxide (DiCup 40C), in parts by weight per 100 parts by weight of polymer, was added as shown in Table X. The compounds were vulcanized by heating at 1600C for 30 minutes.

The vulcanizate properties, shown in Table X, clearly demonstrate the improved properties found for the silica filled vulcanizates of this invention when compared with the control, Experiment A.

TABLE X Experiment A B C Polymer wt. 100 100 100 Silica wt. 50 50 50 Sodium Ammonium stearate salicylate Additive wt. - 2 2 Heat treat - 3 minutes at 1500C on mill Dicumyl peroxide wt. 4 4 3.5 Vulcanize - heat at 1600C for 30 minutes Vulcanizate properties Tensile strength (kg/cm2) 306 260 335 Elongation % 450 380 490 100% Modulus kg/cm2 35 31 25 300% Modulus kg/cm2 180 181 171 25% Modulus kg/cm2 12 9 8 Young's Modulus kg/cm2 146 59 48 Tensile set % 8 4 7 Hardness Shore A2 80 80 75 Example 11 The acrylonitrile-butadiene-hydroxyethyl methacrylate polymer of Example 1 was mixed with silica and a range of additives, as shown in Table XI, subjected to heat treatment, by milling at 1500C for 3 minutes, compounded with dicumyl peroxide (DiCup 40C) and vulcanized by heating for 30 minutes at 1600C, as in Example 1.

The vulcanizate properties are shown in Table XI, from which it is clear that the improved properties are found for each of the additives used in the heat treatment stage. TABLE XI Experiment No. D E F G H I J Additive type I II III IV V VI VII Additive quantity wt. 2 2 2 2 2 2 1.5 Dicumyl peroxide wt. 4 4 4 4 4 4 6 Vulcanizate properties Tensile strength kg/cm2 315 286 300 300 266 300 260 Elogation % 350 320 370 420 360 480 320 100% modulus kg/cm2 35 38 35 30 35 30 40 300% modulus kg/cm2 258 250 228 188 213 159 228 25% Modulus kg/cm2 8 9 9 9 10 9 9 Young's Modulus kg/cm2 54 54 57 61 74 71 58 Tensile set % 4 4 5 4 4 7 5 Hardness Shore A2 77 77 78 77 78 78 79 I - sodium stearate IV - zinc stearate VII-p-toluene sulphonic acid II - potassium stearate V - ammonium stearate III - calcium stearate VI - stearic acid Example 12 Using a polymer similar to that of Example 1, compounds were prepared containing, per 100 parts by weight of polymer, 60 parts by weight of silica, 15 parts by weight of di-octyl phthalate and two parts by weight of the additives shown in Table XII. These compounds were heat treated by milling at 1500C for 3 minutes.On cooling, further compounding ingredients were mixed in on a cool (about 40"C) rubber mill as follows, all being parts by weight per 100 parts by weight of polymer: zinc oxide 5, stearic acid 1.5, benzothiazyl disulphide 1.5, tetramethyl thiuram disulphide 0.5 and sulphur 1.75. These compounds were vulcanized by heating at 166"C for 15 minutes.

The vulcanizate properties are given in Table III. The improved vulcanizate properties are found with all the additives used with the sulphur vulcanization system.

TABLE XII Experiment No. K L M N O Additive type 1 2 3 4 5 Valcanizate properties Tensile strength kg/cm2 274 273 282 281 273 Elongation % 570 560 560 530 540 100% Modulus kg/cm2 15 17 20 20 20 300% Modulus kg/cm2 105 105 108 125 115 25% Modulus kg/cm2 7 7 7 8 7 Young's Modulus kg/cm2 65 68 98 83 67 Tensile set % 15 16 11 13 12 Hardness Shore A2 75 75 74 77 74 1 - sodium stearate 4 - stearic acid 2 - potassium stearate 5 - oleic acid 3 - zinc stearate Example 13 Samples of the polymer of acrylonitrile, butadiene and hydroxyethyl methacrylate of Example 1 were mixed with 50 parts by weight, per 100 parts by weight of polymer, of silica and the amounts of magnesium oxide, in parts by weight per 100 parts by weight of polymer, shown in Table XIII.These compounds were then heat treated by milling on a rubber mill at 1500C for 3 minutes. After being cooled, the compound was put onto a cool (about 40"C) rubber mill and dicumyl peroxide (DiCup 40C) was added and thoroughly mixed in in the amounts, as parts by weight per 100 parts by weight of polymer, shown in Table XIII.

The compounds were then vulcanized by heating at 1600C for 30 minutes and the vulcanizate properties were determined, the results being shown in Table XIII. At 1 part of magnesium oxide a reduction is noted in the Young's modulus; at 5 parts of magnesium oxide, the Young's modulus, tensile set and hardness are markedly reduced and the 300% modulus is markedly increased.

TABLE XIII Experiment No. 131 132 133 134 135 Magnesium oxide wt. 0 1 2 5 10 Dicumyl peroxide wt. 4 4 5 4 3.5 Vulcanizate properties Tensile strength kg/cm2 311 341 274 294 333 Elongation % 420 450 320 350 360 100% modulus kg/cm2 40 40 52 45 45 300% Modulus kg/cm2 208 206 253 250 279 25% Modulus kg/cm2 13 12 14 12 12 Young's Modulus kg/cm2 146 126 125 94 90 Tensile set % 7 9 5 5 6 Hardness Shore A2 82 80 82 79 78 WHAT WE CLAIM IS: 1.A process for the production of a filled rubbery vulcanizate, which comprises shear mixing at a temperature of 100 to 175"C a mixture of 100 parts by weight of a vulcanizable polymer containing, per 100 grams thereof, from 1.5 to 80 millimoles of hydroxyl groups, from 5 to 100 parts by weight of filler selected from silica and calcium silicate, and an additive, cooling the mixture, incorporating into the mixture vulcanization active compound and vulcanizing by heating, wherein the additive comprises from 0.5 to 5 parts by weight, per 100 parts by weight of polymer, of an amine selected from compounds of the formulae R-NH2, R-NHR' and R-NR"R"' wherein R is C4 30 alkyl or alkenyl which may contain up to three NH2, NH or NR" groups, C4 30 cycloalkyl or C7 20 aralkyl, R' is C4.30 alkyl or alkenyl and R' and R"' are the same or different Cl l0 alkyl.

2. A process for the production of a filled rubbery vulcanizate which comprises shear mixing at a temperature of 100 to 175"C a mixture of 100 parts by weight of a vulcanizable polymer containing, per 100 grams thereof, from 1.5 to 80 millimoles of hydroxyl groups, from 5 to 100 parts by weight of filler selected from silica and calcium silicate, and an additive, cooling the mixture, incorporating into the mixture vulcanization active

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (22)

1. **WARNING** start of CLMS field may overlap end of DESC **.

   Example 13 Samples of the polymer of acrylonitrile, butadiene and hydroxyethyl methacrylate of Example 1 were mixed with 50 parts by weight, per 100 parts by weight of polymer, of silica and the amounts of magnesium oxide, in parts by weight per 100 parts by weight of polymer, shown in Table XIII. These compounds were then heat treated by milling on a rubber mill at 1500C for 3 minutes. After being cooled, the compound was put onto a cool (about 40"C) rubber mill and dicumyl peroxide (DiCup 40C) was added and thoroughly mixed in in the amounts, as parts by weight per 100 parts by weight of polymer, shown in Table XIII.

   The compounds were then vulcanized by heating at 1600C for 30 minutes and the vulcanizate properties were determined, the results being shown in Table XIII. At 1 part of magnesium oxide a reduction is noted in the Young's modulus; at 5 parts of magnesium oxide, the Young's modulus, tensile set and hardness are markedly reduced and the 300% modulus is markedly increased.

   TABLE XIII Experiment No. 131 132 133 134 135 Magnesium oxide wt. 0 1 2 5 10 Dicumyl peroxide wt. 4 4 5 4 3.5 Vulcanizate properties Tensile strength kg/cm2 311 341 274 294 333 Elongation % 420 450 320 350 360 100% modulus kg/cm2 40 40 52 45 45 300% Modulus kg/cm2 208 206 253 250 279 25% Modulus kg/cm2 13 12 14 12 12 Young's Modulus kg/cm2 146 126 125 94 90 Tensile set % 7 9 5 5 6 Hardness Shore A2 82 80 82 79 78 WHAT WE CLAIM IS: 1.A process for the production of a filled rubbery vulcanizate, which comprises shear mixing at a temperature of 100 to 175"C a mixture of 100 parts by weight of a vulcanizable polymer containing, per 100 grams thereof, from 1.5 to 80 millimoles of hydroxyl groups, from 5 to 100 parts by weight of filler selected from silica and calcium silicate, and an additive, cooling the mixture, incorporating into the mixture vulcanization active compound and vulcanizing by heating, wherein the additive comprises from 0.5 to 5 parts by weight, per 100 parts by weight of polymer, of an amine selected from compounds of the formulae R-NH2, R-NHR' and R-NR"R"' wherein R is C4 30 alkyl or alkenyl which may contain up to three NH2, NH or NR" groups, C4 30 cycloalkyl or C7 20 aralkyl, R' is C4.30 alkyl or alkenyl and R' and R"' are the same or different Cl l0 alkyl.
2. 2. A process for the production of a filled rubbery vulcanizate which comprises shear mixing at a temperature of 100 to 175"C a mixture of 100 parts by weight of a vulcanizable polymer containing, per 100 grams thereof, from 1.5 to 80 millimoles of hydroxyl groups, from 5 to 100 parts by weight of filler selected from silica and calcium silicate, and an additive, cooling the mixture, incorporating into the mixture vulcanization active

   compound and vulcanizing by heating, wherein the additive comprises from 1 to 5 parts by weight, per 100 parts by weight of polymer, of an acid selected from C150 saturated or unsaturated fatty acids, aromatic carboxylic acids and aryl sulphonic acids, and the alkali metal, alkaline earth metal, zine and ammonium salts of the fatty or carboxylic acids.
3. 3. A process for the production of a filled rubbery vulcanizate, which comprises shear mixing at a temperature of 100 to 175"C a mixture of 100 parts by weight of a vulcanizable polymer containing, per 100 grams thereof, from 1.5 to 80 millimoles of hydroxyl groups, from 5 to 100 parts by weight of filler selected from silica and calcium silicate, and an additive, cooling the mixture, incorporating into the mixture vulcanization active compound and vulcanizing by heating, wherein the additive comprises from 1 to 10 parts by weight per 100 parts by weight of polymer, of magnesium oxide.
4. 4. A process according to claim 1 wherein the amine is selected from compounds of the formulae RNH2 and R-NHR' wherein R is C10-20 alkyl or alkenyl which may contain one NH2 or NH group and R' is C100 alkyl or alkenyl.
5. 5. A process according to claim 2 wherein the additive is selected from palmitic acid, stearic acid, oleic acid, linoleic acid, benzoic acid, phthalic acid, cinnamic acid, hydroxybenzoic acid and the potassium, sodium, calcium, zinc and ammonium salts thereof.
6. 6. A process according to claim 2 wherein the additive is selected from benzenesulphonic acid, toluenesulphonic acid and xylenesulphonic acid.
7. 7. A process according to claim 3 wherein the additive comprises from 5 to 10 parts by weight, per 100 parts by weight of polymer, of magnesium oxide.
8. 8. A process according to any preceding claim wherein the vulcanizable polymer containing hydroxyl groups is selected from essentially C4-C6 conjugated diolefin polymers, copolymers of C4-C6 conjugated diolefins and a least one other copolymerisable vinyl or vinylidene-containing monomer, polymers comprising a C4-C6 isoolefin and polymers comprising one or two alpha olefins.
9. 9. A process according to claim 8 wherein the polymer is selected from butadienestyrene polymers containing hydroxyl groups, butadiene-acrylonitrile polymers containing hydroxyl groups, isoprene-acrylonitrile polymers containing hydroxyl groups and butadiene-methacrylonitrile polymers containing hydroxyl groups.
10. 10. A process according to claim 9 wherein the hydroxyl groups have been incorporated into the polymer by emulsion-free radical copolymerisation with a monomer selected from hydroxyethyl acrylate or methacrylate, hydroxypropyl acrylate or methacrylate, hydroxy propyl crotonate, di(2-hydroxyethyl) maleate or fumarate, N-ethanolacrylamide, hydroxy ethyl vinyl ether and diethylene glycol monovinyl ether.
11. 11. A process according to claim 8 wherein the polymer is selected from polybutadiene containing hydroxyl groups, isobutylene-isoprene polymers containing hydroxyl groups, chlorinated or brominated isobutylene-isoprene polymers containing hydroxyl groups and ethylene-propylene non-conjugated diolefin polymers containing hydroxyl groups.
12. 12. A process according to claim 4 wherein the polymer is a butadiene-styrene or butadiene-acrylonitrile polymer containing a copolymerised monomer selected from hydroxethyl or hydroxypropyl acrylate or methacrylate, and the mixture optionally contains from 5 to 150 parts by weight, per 100 parts by weight of polymer, of additional filler.
13. 13. A process according to claim 5 wherein the polymer is a butadiene-styrene or butadiene-acrylonitrile polymer containing a copolymerised monomer selected from hydroxyethyl or hydroxypropyl acrylate or methacrylate, and the mixture optionally contains from 5 to 150 parts by weight, per 100 parts by weight of polymer, of additional filler.
14. 14. A process according to any preceding claim wherein the mixture is sheared for a time of from 0.25 to 10 minutes.
15. 15. A process according to any preceding claim wherein the silica or calcium silicate has an average particle size of from 0.01 to 0.1 microns.
16. 16. A process according to any preceding claim wherein the shear mixing is conducted by mixing on a rubber mill or in an internal mixer.
17. 17. A process according to any preceding claim wherein the shear mixing at 100 to 175"C is conducted after the mixture has been formed by mixing at a lower temperature.
18. 18. A process according to any preceding claim wherein the polymer is mixed with a like polymer containing no hydroxyl groups in such a proportion that the concentration of hydroxyl groups is from 4 to 60 millimoles per 100 grams of the mixture of polymers.
19. 19. A process according to claim 1 substantially as described in any of Examples 1 to 9.
20. 20. A process according to claim 2 substantially as described in any of Examples 10 to 12.
21. 21. A process according to claim 3 substantially as described in Example 13.
22. 22. A vulcanizate produced by a process according to any preceding claim.