CS198229B2 - Elastoplastic compositions based on thermoplastic polyamide resin and curable rubber - Google Patents

Abstract

1518639 Polyamide-rubber blends MONSANTO CO 2 March 1977 [3 March 1976] 8699/77 Headings C3R and C3M Blends which are elastomeric but processable as a thermoplast can be formulated from (a) a thermoplastic polyamide constituting up to 50 wt. per cent of the composition, (b) a rubber cross-linked to a gel content of at least 80% determined according to U.S. Patent 3,203,937, which is a 1,3-butadiene homopolymer or copolymer with styrene, vinyl pyridine, acrylonitrile and/or metallacrylonitrile, and optionally (c) a plasticizer for (a) in an amount not exceeding that of (a) with (b) + (c) constituting not more than 80 wt. per cent of the composition can be formulated by prescribed procedures which ensure that the cross-linked rubber is preset as very finely dispersed particles in the polyamide matrix; if cross-linking is effected after blending the blend must be masticated without interruption during cross-linking.

Description

The invention relates to thermoplastic compositions and more specifically to thermoplastic elastomeric compositions comprising mixtures of polyamide resin and cross-linked rubber.

Thermoplastics are compositions that can be molded or otherwise shaped and reprocessed at temperatures above their melting or softening point. Thermoplastic elastomers (elastoplasts) are materials that exhibit the properties of both thermoplastics and thermoplastics. elastomers, i.e., they are processed as thermoplastics, but have the physical properties of elastomers. Molded articles can be formed from thermoplastic elastomers by extrusion, injection molding or molding without using the time consuming vulcanization step required with conventional vulcanizates. Eliminating the time required for vulcanizers brings significant manufacturing benefits. Furthermore, thermoplastic elastomers can be reprocessed without having to be regenerated, and in addition many thermoplastics can be heat welded.

Moldable thermoplastic compositions based on nylon and vulcanized rubber having a high nylon content prepared from a tire waste cord, but these compositions are rigid non-elastomeric materials with high rigidity and low elongation. Moldable · thermoplastic compositions based on nylon and vulcanizable rubber having a high content of rubber are also known, and the compositions are vulcanized in a mold using a mold (British Patent Nos. · 866 479 · and No. 1 190 049 and French Patent No. 1,592,857). The present invention relates to moldable thermoplastic elastomeric compositions based on polyamide resin and crosslinked rubber.

The elastoplastic compositions of the invention are compositions comprising, based on 100 parts by weight, the total weight of a resin and a rubber, a mixture of 20 to 50 parts by weight of a thermoplastic polyamide resin; preferably of the polyamide or polylactam type, 80 to 50 parts by weight of rubber crosslinked to a extent corresponding to a rubber gel content of at least 80%, the rubber being a homopolymer. 1,3-butadiene, a copolymer of 1,3-butadiene with styrene, vinylpyridine, acrylonitrile or methacrylonitrile, or mixtures thereof, and optionally 10 to 30% by weight, of a polyamide resin plasticizer, based on the total weight of the composition. These compositions are processable as thermoplastics and are elastomeric.

Preferred compositions according to the invention are mixtures wherein the amount of rubber exceeds the amount of polyamide resin, in particular mixtures containing

up to 45 parts by weight of thermoplastic polyamide resin and 80 to 55 parts by weight of rubber. The compositions are elastomeric and are processable as thermoplastics, even if the rubber has been cross-linked to such a degree that it is 80% insoluble in the composition. common. organic solvents. for unvulcanized. rubber, and retain thermoplasticity, even though the rubber is crosslinked to such an extent that it is substantially completely insoluble. Said relative proportions of polyamide resin and rubber are necessary to produce elastomeric compositions with a sufficient amount of rubber and to ensure thermoplasticity with a sufficient amount of resin. If the amount of rubber exceeds about. 80 parts by weight on. 100 parts total weight - resin and rubber, resin is not present in sufficient quantity for. ensuring thermoplasticity. When the amount of rubber in the absence of polyamide resin plasticizer decreases below about 50 parts by weight, per 100 parts by weight of total resin and rubber, or when the amount of resin exceeds 50% by weight of the composition, hard, rigid compositions with reduced toughness are obtained. Compositions of the invention are contemplated as a composition comprising microparticles - cross-linked rubber dispersed in a continuous resin. matrix. Particularly preferred compositions of the invention comprise cross-linked nitrile rubber and are characterized by a toughness in the ratio TS2 / E, where. TS is the tensile strength and - E is the modulus of elasticity, at least 50% higher than the toughness of a similar resin-free plasticizer composition, but wherein - the weight of the resin exceeds the weight of the rubber.

As mentioned, the thermoplastic elastomers - according to the invention are rubber-based compositions in which - the proportion of rubber in the mixture is crosslinked so that the gel content is - 80% or more - and a crosslink density of 3 x - 10 ~ ⁵ - is achieved - or more moles - per cm ³ - rubber. A suitable procedure for evaluating the crosslink density depends on the individual components present in the compositions. The properties of the compositions can be improved by further cross-linking the rubber until substantially its complete vulcanization is usually indicated by a gel content of 96% or more. In view of this, however, the substantially complete gelation of the 96% - (or - more) is not always a necessary criterion for complete product vulcanization for differences in molecular weight, molecular weight distribution and other variables in diene rubbers, which affects gel determination . Determination of the density - transverse bond of rubber is an alternative means of determining the degree of vulcanization of the vulcanizate, but must be carried out indirectly because the presence of the resin interferes with the determination. Accordingly, - the same rubber as present in the mixture is treated - under conditions, with respect to - the time, - the temperature and the amount of vulcanizing agent at which the product is not fully vulcanized, as indicated by its cross-link density, and this density is assigned to a similarly treated mixture. Transverse densities - bonds of about 7 x 10 ~ ⁵ or more moles - (number of cross-bonds divided by Avogadr number) per - cm3 rubber are typical values for fully vulcanized nitrile rubber, but may reach as low as about 5 x 10 ^s , especially polybutadiene rubber or polybutadiene - styrene rubber. Influencing the vulcanization of the mixture represents a very substantial improvement in the mechanical properties, and this improvement is directly related to its practical application. Surprisingly, elastomeric compositions with such high strength are still thermoplastic over thermosetting elastomers.

Vulcanizable rubbers, although thermoplastic in the unvulcanized state, are normally classified as thermosetting because they undergo heat curing and become unprocessable. The products of the present invention, although processable, are prepared from rubber-resin mixtures that are treated for a period of time and at a temperature such that they are treated. has achieved crosslinking of the rubber or vulcanizing agents in an amount and for a time and at a temperature representing the known conditions for obtaining the vulcanized products by static vulcanization of the rubber by molding, but the rubber undergoes gelatinization to the extent characteristic of the rubber itself. The use of thermosets in the compositions of the present invention should be avoided while simultaneously masticating and vulcanizing the compositions. Thus, for example, the thermoplastic compositions of the present invention are preferably prepared by mixing a mixture of rubber, polyamide resin and optionally vulcanizing agents, followed by masticating the mixture at a temperature sufficient to form a crosslink, using conventional masticating devices such as a kneading machine. - Banbury - - or Brabender,. or - certain extruders adapted for mixing. The resin and rubber are mixed at a temperature sufficient to soften the polyamide resin, or more generally at a temperature above its melting point, if the resin is crystalline at normal temperatures. After the resin and rubber have been thoroughly mixed, the vulcanizing agent is added if necessary. - Heating and - mastication at vulcanization temperatures - generally sufficient - to complete cross-linking - within minutes. or i - shorter times, but shorter times may be required if higher temperatures are desired. A suitable cross-linking temperature range is from about the melting point of the polyamide resin to the decomposition temperature of the rubber, which is generally from about 150 ° C to about 270 ° C, the maximum temperature varying somewhat depending on the type of rubber, the presence of anti-degrading agents. mixing time. A typical range is about. from 160 to 250 ° C, and a temperature range of about 180 to 230 ° C is preferred. In order to obtain thermoplastic compositions, it is important that stirring is continued without interruption until crosslinking occurs. By allowing relatively large crosslinking to occur after stirring is complete, thermosetting unprocessable compositions can be obtained. Those skilled in the art will need several simple experiments using suitable rubbers and vulcanization systems to determine their usefulness in preparing the improved products of the invention.

Methods other than dynamic vulcanization of rubber-resin mixtures may be used to prepare the compositions of the invention. For example, the rubber can be completely vulcanized in the absence of a resin, either dynamically or statically, pulverized and mixed with. resin at a temperature above its melting or softening point. Provided that the crosslinked rubber particles are small, well dispersed and at a suitable concentration, compositions within the scope of the invention can be readily obtained by mixing the crosslinked rubber and resin. Accordingly, the term " mixture " herein refers to a composition comprising well dispersed small particles of crosslinked rubber. The composition outside the scope of the invention, since it contains rubber particles insufficiently dispersed or too large, can be comminuted by two-roll cold processing (to reduce the particle size below about 50 microns, preferably below 20 microns and especially below 5 microns). After sufficient comminution or pulverization, the compositions of the invention are obtained. Often, the deficiencies in dispersion and oversized rubber particles are clearly evident to the naked eye and can be observed on the pressed plates. This occurs especially in the absence of pigments and fillers. In this case, pulverizing and repressing yields a plate in which rubber particle aggregates or large particles are not visible or are much less obvious to the naked eye and the mechanical properties are greatly improved.

All of the compositions of the invention can be formulated in a kneading machine to produce products which, upon transfer to a rotating roller of a rubber twin roll at temperatures above the softening points or crystallization points of the resin phase, form continual plates. The plates can be reprocessed in a kneading machine after temperatures above the softening or melting points of the resin phases have been reached. The material is again brought to a plastic state (molten resin phase state), but by allowing the molten product to pass through the rollers of a rubber twin roller, a continuous plate is formed again. In addition, the plate of the thermoplastic composition of the present invention can be cut into pieces and pressed to give a single smooth plate with perfect bonding or fitting between the pieces. A thermoplastic composition in the foregoing sense is meant herein. In addition, the elastoplastic compositions of the present invention can be further processed such that they can be made by extrusion or injection molding.

If a suitable measure of the degree of vulcanization is the determination of the extractable fraction, the improved elastoplastic compositions are obtained by crosslinking the mixtures to such a extent that the composition contains no more than 20% by weight of the extractable solvent at room temperature. % by weight of extractable rubber and particularly preferably less than 2% by weight of extractable rubber. In general, for non-self-vulcanizing rubber, the lower the extractable content, the better its properties, while for self-vulcanizing rubber it will acquire conventional properties when the extractable fraction is up to 20%, but more preferred compositions with either non-self-vulcanized rubber or with self-vulcanizing rubber there are those having a low extractable rubber content. The gel content, expressed as% gel, was determined by the method of U.S. Patent No. 3,203,937, which determined the amount of insoluble polymer by soaking the sample in a rubber solvent for 48 hours at room temperature and weighing the dried residue, making appropriate corrections based on knowledge of composition. Thus, corrected initial and final weights are obtained by subtracting from the initial weight the weight of soluble components other than rubber, for example extender oils, plasticizers and resin components soluble in the organic solvent. Insoluble pigments, fillers, etc. are subtracted from both initial and final weights.

When using cross-link densities as a measure of the degree of vulcanization that characterizes the improved elastoplastic compositions, the mixture is crosslinked to an extent that corresponds to the crosslinking of the same rubber present in the mixture and which is statically crosslinked under pressure in a press using an amount of the same optional vulcanizing agent present in the mixture and at such a time and temperature as to achieve an effective crosslink density of greater than 3 x 10 ^-5 moles per cm ^{3 of} rubber and more than 5 x 10 ^-5 or even more preferably 1 × 10 ^-4 moles per cm ^{3 of} rubber. The mixture is then dynamically crosslinked under similar conditions (with the same amount of vulcanizing agent, if any, depending on the rubber content of the mixture) required for the rubber itself. The crosslink density thus determined can be considered as a measure of the extent of vulcanization that provides improved thermoplastics. However, it should not be assumed - based on the fact that the amount of vulcanizing agent depends on the rubber content in the mixture and that it is the amount providing the above crosslink density with the rubber itself - that the vulcanizing agent does not react with the resin or that there is no reaction between the resin and the rubber. . Very significant reactions can take place, but to a limited extent. However, the assumption that the crosslink density determined as described above represents a useful approximation to the crosslink density values of the elastoplastic compositions is related to the thermoplastic properties and the fact that a large proportion of the resin can be removed from the mixture by extraction with a resin solvent such as formic acid.

The transverse bond density of the rubber is determined by equilibrium swelling in the solvent using the Flory-Rehner equation (J. Rubber Chem. And Tech., 30, p. 929). Suitable Huggins solubility parameters for the rubber-solvent pair used in the calculation were obtained from a review by Sheehan and Bisio in J. Rubber Chem. and Těch., 39, 149. If the extracted gel content of the vulcanized rubber is low, a Bueche correction must be used where the _r- member is multiplied by the gel fraction (% gel / 100). The crosslink density is half the effective chain density of the network in the absence of resin. Therefore, the crosslink density of the vulcanized compositions is further understood to be the value determined in the manner described above with the same rubber as the composition. Even more preferred mixtures meet both the above-described measures of the degree of vulcanization, namely the determination of the crosslink density and the percentage of extractable rubber.

A suitable rubber for the process of the invention is a substantially irregular, non-crystalline, rubbery polymer from the group of 1,3-butadiene homopolymer, 1,3-butadiene copolymer with styrene, vinylpyridine, acrylonitrile or methacrylonitrile, or a mixture of said homopolymer with one or more of said copolymers; mixtures of two or more of said copolymers. Commercially available rubbers suitable for the process of the invention are described in Rubber World Blue Book, 1975, Materials and Compounding Ingredients for Rubber, respectively: nitrile rubber on pages 416-430, polybutadiene rubber on pages 431-432, and styrene. butadiene rubber on page 452—460. Preference is given to copolymers of 1,3-butadiene with about 15 to 60% acrylonitrile, commonly called nitrile rubber. Both nitrile and non-self-vulcanizing rubbers are suitable for use in the present invention. Nitrile rubbers not subject to self-vulcanization require, as their name implies, the presence of vulcanizing agents in order to crosslink the rubber at processing temperatures to such an extent that the rubber gel content is at least about 80% or more. The self-vulcanizing nitrile rubber, as indicated by its name, will crosslink at processing temperatures in the absence of vulcanizing agents (other than vulcanizing agents that may be naturally present) to such an extent that the gel gel content is at least about 80% or more. Compositions of the invention based on mixtures wherein the rubber component is a self-vulcanizing nitrile rubber generally exhibit improved tensile strength and are therefore preferred. The self-vulcanizing nitrile rubber compositions can be further crosslinked using conventional vulcanizing agents as described below, which usually leads to a further increase in the tensile strength of the resulting composition.

Whether or not the nitrile rubber is self-vulcanizing does not depend on the acrylonitrile content or the Mooney viscosity, but is probably a natural property of certain rubbers. A suitable means for determining the self-vulcanizability of a nitrile rubber is by subjecting the rubber to a Brabender kneading machine at a temperature of 225 ° C and observing its tendency to vulcanize. Self-vulcanizing nitrile rubbers typically vulcanize under the above conditions within 2 to 8 minutes, while rubbers not subject to self-vulcanization can generally be subjected to the above treatment for 20 minutes or more without vulcanizing them. In the above vulcanization, the rubber loses its ability to continuously maintain the fluidity of the mass in the kneading machine and instead disintegrates into fine particles with a certain amount of pulp in the form of particles that fall out of the kneader throat when the upper wedge is lifted. The vulcanized rubber or the rubber subjected to 20 minutes of mastication as described above is swung out of the kneading machine, pressed at 230 ° C for 5 minutes and the gel content determined by extraction into dichloromethane at room temperature. For self-vulcanizing rubber, the gel content will be about 80% or more (the weight of the extractable fraction is 20% or less), while the non-self-vulcanizing rubber will have a gel content of less than 80%.

Suitable thermoplastic polyamide resins (nylon) are solid polymers of crystalline or resinous nature having high molecular weight and repeating amide units in the polymer chain. Polyamide resins may be prepared by polymerizing one or more ε-lactams, for example caprolactam, pyrrolidone, lauryllactam and aminoundecanoic acid lactam, and condensing dibasic acids and diamines. Nylon fibers of both fiber-forming and compression types are suitable. Examples of these resins are: caprolactam (nylon-6), polylauryllactam (nylon-12), poly (nylon-6,6), polyhexamethylenamide adipic acid (nylon-6,6). azelaic acid polyhexamethylenamide (nylon-6,9), sebacic acid polyhexamethylenamide (nylon-6,10),. polyhexamethylenisophthalamide. (Nylon-6, IP). and the 11-aminoundecanoic acid (nylon-11) condensation product. Other examples of suitable polyamide resins (especially those whose softening point is below 275 ° C) are described in Kirk-Othmer, Encyclopedia of Chemical Technology, Vol. 10, p. 919 and the Encyclopedia of Polymer. Science and Technology, Vol. 10, pp. 392-414. In the process according to the invention it is possible to s. advantageously to use commercially available thermoplastic polyamide resins with linear polyamide resins whose preferred softening temperature range. or melting at 160-230 ° C.

The individual results obtained in the above procedure are dynamic. vulcanizations are a function of the individual vulcanization system chosen for the rubber. For the preparation of the improved thermoplastic materials of the invention, vulcanizing agents and vulcanizing systems are commonly used for vulcanizing diene rubbers. Any vulcanizing agent or vulcanizing system suitable for vulcanizing diene rubbers such as peroxide, azide and the like can be used in the process of the invention. quinoid vulcanization systems. or accelerated sulfur. Combinations of maleimide and a peroxide or disulfide accelerator may be used. . Suitable vulcanizing agents and vulcanizing systems are incorporated herein by reference in U.S. Patent No. 3,806,558 (Columns 3-4). Sufficient amounts of vulcanizing agents are used to achieve substantially complete vulcanization of the rubber as determined by increasing tensile strength, crosslink density, sol content (percentage of extractable fraction), or combinations thereof. Care should be taken. the use of excess amounts of vulcanizing agents, since amounts considerably higher than necessary for complete vulcanization of rubber may result in deterioration of properties, for example, ductility values. Preferably, peroxide curing agents are used in minor amounts together with other curing agents such as sulfur or sulfur. bis-maleimide, provided that the total amount of vulcanizing agent is sufficient to completely vulcanize the rubber. High energy radiation can also be used as a vulcanizing agent.

In particular, curing systems containing bis-maleimide are recommended. Effective or semi-active sulfur vulcanization systems having high accelerator / / sulfur ratio values as well as conventional sulfur vulcanization systems in which the amount of sulfur exceeds the amount of accelerator are also particularly recommended.

One aspect. of the invention is the addition of a polyamide resin plasticizer. to. The plasticizer used extends the range of proportions of resin in the mixture while mixing. preserves elastoplasticity. For example, without the use of a resin softener, the weight of the resin cannot exceed the weight of the rubber without occurring. loss of rubbery elasticity, whereas when using a plasticizer, the weight of the resin may exceed the weight of the rubber to such an extent that the amount of resin does not comprise more than 50% by weight of the total composition. and the weight of the plasticizer does not exceed the weight of the resin. Typically, the amount of polyamide resin plasticizer optionally present is 10 to 30% by weight, based on the total composition. Any polyamide plasticizer may be used. resin. . Sulfonamide-type plasticizers are an important class of plasticizers. polyamide resins such as N-butylbenzenesulfonamide, N-cyclohexyl-p-toluenesulfonamide, o, p-toluenesulfonamide; N-ethyl-o, p-toluenesulfonamide and N-ethyl-o-toluenesulfonamide.

Others. An aspect of the invention is the addition of an anti-inflammatory agent. aging the rubber to the mixture prior to dynamic vulcanization. The presence of this. of the composition protects the mixture from thermal and / or oxidative degradation, so that mixtures with excellent ones are obtained. properties. Preferably, an anti-aging agent is added to the rubber. start of the mixing cycle. and for greater effect. more preferably, the anti-aging agent is added in the preparation of the rubber premix and part of the premix. containing. rubber and. anti-aging agent. se. stir. with resin. Resin .. then. melts. a. 'po. . completion of mixing the composition. . subjected to the above-described dynamic vulcanization. Appropriate means of preventing. aging rubber. is reported in the Rubber World Blue Book. (see above), pp. 107-140.

Properties of elastoplastic materials. compositions according to. The invention can be modified either before or after vulcanization by addition. the ingredients of which. usually. used in assembling-mixtures on. diene rubber base, polyamide resin or mixtures thereof. . Examples of these. The additives are carbon black, silica, titanium dioxide, colored. pigments, clay, zinc oxide, stearic acid, accelerators, vulcanizing agents, sulfur, stabilizers, antifouling agents. aging, processing means, adhesive means, means. for improvement . tack tack, rubber softeners, wax, pre-vulcanization inhibitors, discontinuous fibers such as wood pulp fibers. and extender oils. Particularly preferred is the addition of carbon black, a plasticizer, or both, preferably. before dynamic vulcanization. Rather, the procedure is preferred,. wherein the carbon black and / or rubber softener is added to the rubber in the preparation of the premix, and the premix is then mixed. with resin.

8 2. 29

In elastoplastic compositions, the addition of carbon black improves tensile strength and the addition of a rubber softener may improve oil swelling resistance, thermal stability, hysterosis, cost and permanent deformation. Aromatic, naphthenic and paraffinic extender oils are suitable plasticizers for rubbers of the type. polybutadlene and butadlene-woollarene. Plasticizers can also improve processability. As regards suitable extender oils, it states. with a link to the publication. Rubber World Blue Book (see above), pp. 145—190. The amount of extender oil to be added depends on the desired properties, the upper limit being dependent on the compatibility of the individual oil and the ingredients of the mixture, and this limit is exceeded when the extinction of the extender is effected. .. oils. A typical addition of extender oil is 5 to 75 parts by weight. adjustment oil per 100 parts, wt. rubber and polyamide resins. Typically, about 10 to 60 parts are added. 20 to 50 parts by weight of extender oil per 100 parts by weight of rubber are preferred. - Typical additions. the carbon black is in the range of about 20 to 100 parts by weight, the carbon black per 100 parts by weight of rubber, and usually about 25 to 60 parts by weight of carbon black. It puts on 100 parts of total - weight of rubber and extender oil. Qty. the soot which can be used depends on. at least in part, on the type. the soot and amounts used. the extender oil used. The amount of extender oil depends, at least in part, on the type of rubber. Kaučuky s. high viscosity. can be adjusted to a higher oil content. Pro. nitrile rubber is usually used in place of the extender oil of the polyvinyl chloride type plasticizer.

The elastoplastic compositions of the present invention are useful for. production of various products, such as penumatics,. hoses, belts, seals, molded rubber and moldings. The products of said mixtures are mainly produced by extrusion,. injection molding and pressing. Mixtures are. also useful for modifying thermoplastic resins, especially polyamide resins. Mixtures of the compositions of the invention with thermoplastic resins are prepared using conventional mixing equipment. Modified properties. the resin depends on the amount of the elastoplastic composition. Usually it is such an amount that it is modified. the resin contains 5 to 50 parts by weight of rubber to about 95 to 50 parts by weight of the total resin. .

Tensile properties of compositions. are determined in accordance with the test procedures of ASTM D 638 and ASTM D 1566. The approximate toughness is calculated by abbreviation. Griffith equation (TS.) ² / / E (TS = tensile strength, E = elastic modulus). ,

Refer to the publication for details

Fracture, redacted. H. Llebowitz a. published by Academie. Press, New

York, 1972, Chapter. 6,. Fracture of. Elastomers by A. N. Gent. . The compositions are elastomeric, processable. as thermoplastics and can be reprocessed without having to be regenerated to. as opposed to conventional thermosetting vulcanizates. The term " elastomeric " as used herein and in the definition of the present invention refers to a composition having a penetrating ability to contract. back within 1 minute to less than 60%. its original length after stretching at room temperature to double its. length and after standing for 1 minute before relieving. This definition closely resembles the definition for rubber mentioned. in American standards ASTM, Vol. 28, p. 756 (D1566): “Rubber in your own. the modified state, without solvents, withdraws back during. 1 minute to less than 1.5 times its original length, after stretching at room temperature. (20 to 27 ° C) to twice its length. and left to stand still. The compositions according to the invention which are particularly preferred are rubber-based compositions having a tensile stiffness value of about 50% or less. More preferred are rubber-based compositions with hardness. 60 (or lower) Shore D, or 100% module. 16,0 MPa or. lower, or with a modulus of elasticity below 200.0 MPa.

Examples

Typical. The process for preparing the elastoplastic compositions of the present invention is carried out by rubber and polyamide. the resins are mixed in the indicated proportions in a Brabendera kneading machine at an oil bath temperature as described below for a time sufficient to melt the resin and form a mixture, usually in the range of 2 to 6 minutes. In the following, the mixing temperature is understood to be the temperature of the oil bath, it being understood that the actual temperature. mixture can. vary. If it is. for example, vulcanizing agents are added. rubber strengthening and mixing agents. continues until maximum consistency in the Brabender kneading machine is reached, usually for 1. up to 5 minutes, and then 2 minutes. The order of mixing may vary, but all ingredients are to be added. and blend before substantial vulcanization occurs. The vulcanized but thermoplastic composition is removed, processed into plates on a double roll (or compressed in a press), transferred back to a Brabender kneading machine, and mixed at the same temperature for 2 minutes. The mass is reprocessed into plates and then pressed at 200 to 270 ° C and cooled to below 100 ° C under pressure before removal. The properties of the molded plate are measured and recorded. In the examples below, the above procedure is followed unless otherwise indicated.

The ingredients used in the compositions of the invention are: N'- (1,3-dimethylbutyl) -N'- (phenyl-p-phenylenedlamine. (Santoflex.RTM. 13 - anti-aging agent), polymerized. 1,2-dihydro (Flectol). H-anti-aging), m-phenylene-bls-maleimide (HVA-2), 2- (morpholmothio) benzothiazole (Santocure®-MOR accelerator), tetramethylthiuram disulfide (TMTD) and 2-bis-benzothiazyldisulfide (MBTS). Tables I to IX illustrate the composition of the compositions of the invention and their properties.

The data in Table I are compositions of the invention comprising 66.7 parts by weight of nitrile rubber and 33.3 parts by weight of polyamide resin. The polyamide resin is Nylon 6.9, azelaic acid polyhexamethylenamide having a melting point of 210 ° C, which is a condensation product of hexamethylenediamine and azelaic acid or an ester thereof. The nitrile rubber designated A is a copolymer not subject to self-vulcanization, namely a copolymer of 1,3-butadiene and 41% by weight, acrylonitrile, with a Mooney viscosity (ML + 4) = 60. The nitrile rubber designated B is a self-vulcanizing copolymer of 1,3-butadiene; 41 weight percent acrylonitrile, Mooney viscosity (MI 1 + 4) = 80. Nitrile rubber B, if heated. alone at 225 ° C, undergoes self-vulcanization (vulcanized within 5 minutes) to such an extent that the rubber gel content is about 85% (15% by weight, the rubber can be extracted into dichloromethane).

Elastoplastic compositions are prepared according to typical techniques. procedure described. above at 210 ° C in. by a Brabender kneading machine and at a mixing speed of 80 rpm. minute. Before adding the curing agent (HVA-2). is added a means against. aging rubber. (0.67 parts by weight).

Flectol H). The compositions of mixtures 1 and 7 do not contain a vulcanizing agent, whereas in mixtures 2 to 6 and 8 to 12 the amount of vulcanizing agent (HVA-2) added. changes. The values of Table 1 show that the properties of the rubber-free compositions not subject to self-vulcanization are greatly improved by the addition of a vulcanizing agent. An increase in tensile strength (TS) of 100% or more is achieved by adding 0.67 parts by weight of the vulcanizing agent, and the properties are further improved with increasing amounts of vulcanizing agent. The toughness, expressed as the ratio (TS) 2 / e, increases after the addition of the vulcanizing agent and further increases up to. 5.33 parts by weight of vulcanizing agent. Mixture 7 illustrates a composition of the invention prepared from a self-vulcanizing nitrile rubber, which composition has excellent properties, in particular high toughness. The addition of a vulcanizing agent results in compositions having only a slightly higher strength but a substantially higher stiffness. The toughness of the composition decreases as the content of the vulcanizing agent increases.

TABLE I

Mixture Nitrile Vulk. agent Strength 100% Module Toughness Ductility no. rubber (HVA-1) in turn module flexibility (TS) ² / E % parts (TS) MPa MPa (E) MPa MPa

1 AND 0 4.9 2 AND 0.67 11.1 3 AND 1.33 14.4 4 AND 2.67 14.6 5 AND 5.33 17.4 6 'A 10.67 17.7 7 (B) 0 19.9 8 (B) 0.17 21.0 9 (B) 0.35 21.2 10 (B) 0.67 23.3 11 (B) 1.33 2.67 23.6 12 (B) 20.0 Mixture no. 1 to 6 comprises nitrile rubber

Type B rubber

4.3 10.0 2.4 180 10.2 47.7 2.6 120 11.5 72.0 2.9 170 12.2 66.9 3.2 150 15.3 87.6 3.5 130 16.3 119.4 2.6 110 9.5 49.1 8.1 360 10.3 60.1 7.3 330 10.5 61.1 7.4 330 11.6 90.8 6.0 310 12.0 95.7 5.8 340 14.0 127.1 3.1 200

type A and mixture no. Figures 7 to 12 contain nitrite. Table II illustrates the elastoplastic compositions of the present invention containing 15 different nitride rubbers not subject to self-vulcanization. The polyamide resin is the same as in Table I and the compositions are prepared in the same manner. All compositions contain 66.7 parts by weight, rubber, 33.3 parts by weight. Nylon - 6.9, 0.67 parts by weight. In addition, 0.67 parts by weight of Flectol H and vulcanized compositions are still present. HVA-2. For nitrile rubber, the table below lists acrylonitrile (AN) content and Mooney viscosity. Odd numbered mixtures are control mixtures containing an anti-aging agent but no vulcanizing agent and even numbered compositions illustrate compositions of the invention in which the rubber is crosslinked by mastication with the addition of a curing agent at 210 ° C for 6 to 8 minutes. . Composition. are then pressed to. Plates of about 2 to 3 mm in thickness at 255 ° C; and. it is cooled under pressure before being removed. Content . The gel ("% by weight, " insoluble in methylene chloride) of the cure-free compositions was determined. with the same rubber and under similar conditions,

8 22 9

II but in the absence of resin. The crosslink density of the compositions containing the vulcanizing agent is greater than 7 x 10 ⁵ moles per cm ^{3 of} rubber. The values in the table indicate that the addition of the vulcanizing agent causes a substantial increase in tensile strength, generally by 100% or more. Compositions containing vulcanized rubber also have higher

U swelling resistance in oil. Oil swelling percentages represent an increase in the size of the oil-soaked sample (1361 g) at 150 ° C for 48 hours. The data in the table indicates that the compositions of the invention can be prepared from all nitrile rubbers regardless of the acrylonitrile rubber content or its Mooney viscosity.

TABLE II

Mixture no. Nitrile. rubber Gel content,% Tensile strength MPa 100% MPa module Toughness (TSp / E MPa % Acrylonitrile content Viscosity Mooney ML 14-4 (100 ºC) 1 22nd 70 59 4.0 - 2.1. 2 9.4 7.7 2.3 3 28 50 61 3.2 - 1,2 4 8.5 7.8 2.2 5 33 25 48 1.7 1.7 0.9 6 7.6 7.0 2.1 7 33 40 74 5.8 3.3 8 9.1 - 0.8 9 33 55 71 5.9 5.6 2.9 10 13.6 10.1 3.5 11 39 47 53 2.2 2.2 1,2 12 7.5 7.0 1.9 13 39 50 64 4.6 4.2 1,8 14 14.4 9.4 4.0 15 Dec 39 57 62 4.4 4.1 1,8 16 13.4 11.2 2,0 17 39 80 70 7.4 6.7 2.6 18 . 16.7 12.1 2.1 19 Dec 41 60 45 4.9 4.3 2.4 20 May 10.6 9.6 1.9 21 41 80 66 7.3 6.3 2.9 22nd 12.8 11.1 1.5 23 45 48 52 5.0 3.9 3.4 24 9.4 9.1 1.7 25 45 60 47 4.1 4.0 1.5 26 13.1 10.3 3.3 27 Mar: 45 60 33 7.5 5.4 3.7 28 13.6 10.8 2.6 29 51 55 61 6.5 - 2.2 30 13.4 - 1.6

Table II - continued

Mixture no. Nítril. rubber Gel content, % Modulus of elasticity MPa Ductility% Swelling in oil,% % Acrylonitrile content Viscosity Mooney ML 1 + 4 (100 ºC) 1 22nd 70 59 7.5 70 42 2 37.8 150 25 3 28 50 61 8.4 80 38 4 32.8 130 25 5 33 25 48 3.4 190 14 6 28.1 120 9 7 33 40 74 10.2 80 20 May 8 108.5 50 17 9 33 55 71 12.0 130 21 10 53.6 200 16 11 39 47 53 3.9 150 14 12 29.1 110 13 13 39 50 , 64 12.0 130 9 14 52.4 240 7 15 Dec 39 57 62 10.9 140 14 16 89.1 180 14 17 39 80 70 21.0 130 17 18 130.3 240 12 19 Dec 41 60 - 45 10.0 180 14 20 May 57.7 120 13 21 41 80 66 18.5 160 11 22nd 109.2 160 11 23 45 48 52 7.4 220 13 24 51.3 110 10 25 45 60 47 11.0 170 2 26 52.4 190 0 27 Mar: 45 60 33 15.3 280 9 28 71.6 210 7 29 51 55 61 19.5 100 ALIGN! 7 30 110.2 90 6

Table III illustrates the elastoplastic compositions of the invention containing 8 different self-vulcanizing rubbers. The odd numbered mixtures comprise 66.7 parts by weight of nitrile rubber, 33.3 parts by weight of nitrile rubber. % Of Nylon 6.9 and 0.67 parts by weight. Flectol H. Even-numbered mixtures contain the same impurities as odd-numbered mixtures but additionally contain 0.67 parts by weight. HVA-2. All mixtures ^; are subjected to a Brabender kneading machine at 210 ° C and a total mixing time of 6 to 8 minutes by a typical procedure as explained above. The compositions are then pressed into sheets 2-3 mm thick at 255 ° C and cooled under pressure before being removed. The gel content (wt% insoluble in methylene chloride) of the compositions without vulcanizing agent is determined with the same rubber and under similar conditions but in the absence of resin. The crosslink density of the compositions containing the vulcanizing agent is greater than 7 x 10 -5 moles per cm 3 of rubber. The data in the table indicates that self-vulcanizing rubbers provide thermoplastic elastomeric compositions with superior properties without the addition of vulcanizing agents. The addition of a vulcanizing agent increases the tensile strength, the 100% modulus and the modulus of elasticity. The properties of the compositions are similar regardless of the acrylonitrile content and the viscosity of the Mooney nitrile rubber present in the composition.

20 May

TABLE III

Mixture no. Nitrll. rubber Gel content,% Tensile strength MPa 100% module MPa Modulus of elasticity MPa % Acrylonitrile content Mooney Viscose ML 1 + 4 (100 ° C) 1 21 80 83 15.0 8.6 52.6 2 15.7 10.4 81.3 3 29 30 81 16.6 9.8 37.9 4 21.7 11.7 101.4 5 33 80 83 17.2 9.0 50.0 6 19.8 11.5 120.1 7 33 95 91 17.9 9.1 36.5 8 19.7 11.4 100.4 9 41 50 89 17.2 9.6 43.2 10 21.8 11.6 91.9 11 41 80 85 19.9 9.5 49.1 12 23.6 12.0 123.8 13 41 95 86 13.8 8.7 30.0 14 15.7 10.7 81.0 15 Dec 43 95 93 18.4 9.5 39.9 16. 20.9 11.6 90.2

TABLE III

Mixture no. Nitrll. rubber Gel content, % Toughness (TS) ² / EMPa Ductility % Swelling in oil% % Acrylonitrile content Mooney ML 1 + 4 Damage (100 ° C) 1 21 80 83 4.3 280 29 2 3.0 230 26 3 29 30 81 7.3 250 27 Mar: 4 4.6 290 21 5 33 80 83 5.9 300 15 Dec 6 3.3 290 16 7 33 95 91 8.8 300 16 8 3.9 250 18 9 41 50 89 6.8 290 11 10 5.2 320 7 11 41 80 85 8.1 360 6 12 4,5 360 5 13 41 95 86 6.3 230 10 14 3.0 240 13 15 Dec 43 95 93 8.5 310 10 16 4.8 270 13

The data in Table IV illustrate compositions containing various proportions of nitrile rubber and polyamide resin. Nitrile rubber is a self-vulcanizing rubber containing 43 why. The polyamide resin is Nylon 6.9. The compositions are prepared in the same manner. step used for the mixtures of Tables I to III. The values of the table show that the tensile strength and modulus decreases with increasing amount of rubber. The data of the table further indicates that the toughness of the compositions given by the (TS) ² / E ratio is substantially the same up to 40 parts by weight of rubber but varies substantially by leaping to reach 50 parts by weight of rubber, and from that value the toughness increases containing rubber.

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Table V illustrates the elastoplastic compositions of the invention containing various polyamide resins. In mixtures 1 and 2, the polyamide resin is polyhexamethyleneisophthalamide having a melting point of 220 ° C (Nylon IP), in mixtures 3 and 4 a polycaprolactam having a melting point of 216 ° C (Nylon 6), in mixtures of Nylon 6 copolymer. and Nylon 6.6 with a melting point of 243 ° C (Nylon 6-6.6) and in mixtures of 6 and 7 polyhexamethylenamide. adipic acid, m.p. 264 DEG C. (Nylon 6.6). The compositions are prepared by a typical procedure.

TABLE V

Mixture no. 1 2 3 4 5 6 7 Nitrile rubber 601 601 601 66.71 602 603 603 Nylon IP 40 40 - - - - - Nylon 6 - - 40 33.3 -. - . - Nylon 6-6,6 - - - - 40 -. '. · - Nylon 6,6 - * - - - - 40 40 HVA-2. 0 2 2 0.67 0.6 - 1,2 Means anti aging 0,6 ⁴ 0.64 0.64 - 0.65 1,2 ^S 1,25 Stirring temperature, ° C 220 220 220 220 250 270 270 Tensile strength, MPa 17.9 27.1 21.8 21.9 15.9 7.4 21.6 100% module, MPa 16.2 21.7 17.7 13.6 14.3 18.4 Modulus of elasticity, MPa 170.7 334.1 168.7 103.4 154.6 82.2 330.5 Elongation,% 150 190 180 260 140 70 180 Toughness '· (TS) 2 / E, MPa 1.9 2.2 2.8 4.6 1.6 0.7 1.4 Shore D hardness - - - 43 46 40 55 Tightening,% - - - 31 49 - 45

Self-vulcanizing nitrile rubber, content. % acrylonitrile 43 wt.%, Mooney viscosity 95.

² Self-vulcanizing nitrile rubber, acrylonitrile content 45% by weight, Mooney viscosity 60. The vulcanization system contains 0.15 parts MBTS.

Self-vulcanizing nitrile rubber, acrylonitrile content 39% by weight, Mooney viscosity 50.

Santoflex · 13.

Flectol H.

Table VI illustrates thermoplastic elastomer compositions of the invention comprising styrene-butadiene rubber. Rubber is a cold polymerized · styrene-bound butadiene-styrene rubber

23.5% and a nominal viscosity of Mooney - 52. Compositions in which the ratio. rubber · á · po- ·; the lyamide resins are converted by the 'typical' process described above. The data in the table suggests that compositions with increasing proportion of Nylon are obtained. with the highest strength and stiffness. Compared to the results obtained with nitrile rubber. the toughness does not increase with an increasing proportion. styrene-butadiene rubber (SBR).

TABLE VI

Mixture no. 1 2 3 4 5 6 SBR-1'502 80 75 70 66.7 60 50 Nylon- 6,9 20 May 25 30 33.3 40 50 HVA-2 0.8 0.75 0.7 0.67 0.6 0.5 Flectol H 0.8 0.75 0.7 0.67 0.6 0.5 Stirring speed, rpm. 80 80 80 80 80 80 Stirring temperature, ° C 210 210 210 210 210 210 Pressing temperature, ° C 255 255 255 255 255 255 Tensile strength,. MPa 6.3 6.9 8.6 10.9 14.9 18.7 100% module, MPa 5.2 6.0 7.5 8.9 10.9 15.2 Modulus of elasticity, MPa 23.9 34.1 53.4 66.4 96.6 160.0 Elongation,% 140 130 140 160 200 200 Toughness (TSJ ² / E, MPa 1.7 1.4 1.4 1,8 2.3 2.2

Table VII clarifies. compositions according to the teach. The compositions are prepared. a typical invention containing a polybutadiene copolymer.

TABLE VII

Mixture no.

2

Polybutadiene rubber ¹ 66.7 - Polybutadiene rubber2 - 66.7 Nylon 6,9 33.3 33.3 Flectol H 0.67 0.67 HVA-2 0.67 0.67 Mixing speed rpm. 80 80 Stirring temperature, ° C 210 210 Tensile strength, MPa 9.8 11.0 100 ¹ % module, MPa 9.1 9.4 Modulus of elasticity, MPa 84.5 743 Elongation,% 120 150 Toughness, (TS) 2 / E, MPa 1.1 1.6

¹ Uncoloured polybutadiene rubber, cis-isomer content 98%, Mooney viscosity 41,

2 · Non-staining polybutadiene rubber, obtained by solution polymerization.

Table VIII illustrates compositions of the invention containing polyamide resin plasticizers. The compositions are prepared in a Brabender kneading machine in a typical manner. The polyamide resin, nitrile rubber and plasticizer are added simultaneously at a stirring temperature of 215 ° C. Stirring. at a speed of 150 rpm until the resin melts and the mixture is then stirred at 80 rpm for 5 minutes. For compositions containing a vulcanizing agent, this is added after a two minute mixing cycle at 80 rpm. The samples are compressed at 225-230 ° C. All parts are expressed by weight.

TABLE VIII

Mixture no. 1 2 3. 4 5 6 Nitrile. rubber ¹ 40 40 40 40 40 40 Nylon 6,9 60 60 60 60 60 60 Anti-aging agent (Flectol H) 0.4 0.4 0.4 0.4 0.4 0.4 N-ethyl-o-t-toluenesulfonamide - - 20 May 20 May 30 40 HVA-2 - 0.4 - 0.4 0.4 0.4 Tensile strength, MPa 25.7 30.1 19.3 24.3 21.7 16.4 1001% module, MPa 22.8 23.3 14.4 15.7 13.3 11.7 Modulus of elasticity, MPa 3-90.5 450.9 149.0 174.8 145.1 130.0 Toughness, (TS) 2 / E, MPa 1.7 2,0 2.5 3.4 3.2 2.1 Elongation,% 210 300 250 310 340 280 Hardness, Shore D, 61 61 49 50 45 43 Tightening,% 68 73 51 56 53 52

Sarhovulcanising nitrile rubber, acrylonitrile content 43% by weight, Mooney viscosity 95.

The data in Table VIII indicates that rigid, hard, non-elastomeric compositions (mixtures 1 and 2) containing a predominant amount of resin as one of the components can be modified by the addition of a resin softener so as to obtain flexible, soft, tougher elastomer compositions. to 6) with a modulus of elasticity of less than 200.0 MPa, a hardness of 50 (Shore D) or less and a tensile shear of less than 60%.

Table IX illustrates compositions of the invention with vulcanizing systems containing sulfur and peroxide. The compositions are prepared by a typical process except that the stirring temperature is 180 ° C and stirred at 150 rpm until the resin (Nylon) melts, and then stirred at 80 rpm. The pressing temperature is 220 ° C. Mixture 1 is a control and does not contain a curing agent. Mixture 2 illustrates a composition prepared with a cure system containing accelerated sulfur. Mixture 3 represents a composition using an activated m-phenylene-bis-maleimide curing system. Mixture 4 illustrates a composition with a peroxide-type curing agent. Composition of mixtures. 3 and 4 are thermoplastic elastomers and exhibit improved properties.

TABLE IX

Mixture no. 1 2 3 4 Nitrile rubber (1) 60 60 60 60 Nylon 6-6,6 (2) 40 40 40 40 Zinc oxide -. 3 - - Stearic acid - 0.3 - - TMTD - 1,2 -, - Santocure - MOR - 0.6 - - Sulfur  - 0.12 - - - HVA-2 . - -. . . 1,8 0.45  - MBTS - - - ' Peroxide (3) - - - 0.3 Tensile strength, MPa 3.2 8.5 8.7. 8.1 100% module, MPa 2.5 7.5 3.8 6.2 Modulus of elasticity, MPa 6.3 34.8 6.5 17.4 Elongation,% 290 160 310 220 Toughness, (TS) ^{1 2} / E, MPa 1.6 72 2.1 11.6 3.8 31 Tightening - in - tension, -% 15 Dec 51 Hardness, Shore D 17 '35 28 32

(1) Self-vulcanized nitrile rubber, acrylonitrile content 39% by weight, Mooney viscosity 50, gel content 65% (on vulcanization without vulcanizing agent, (2) Nylon 6 and Nylon 6,6 copolymer, melting point 160 ° C, (3) 2.5? 1006? -2.5-61-- (tert-butylperoxy hexane (90%)).

The typical examples given to illustrate the invention are not intended to limit it in any way. It is possible to make changes and modifications based on the exemplary procedures of the invention, but this is not a change in the spirit of the invention and does not depart from its scope.

Claims (2)

OBJECT OF THE INVENTION 1. Elastoplastic compositions based on a thermoplastic polyamide resin and a vulcanizable rubber or plasticizers for a polyamide resin and a rubber, usable for the manufacture of shaped articles and for the modification of thermoplastic resins, characterized in that they comprise, based on 100 parts by weight of total by weight of resin and rubber, a mixture of 20 to 50 parts by weight of thermoplastic polyamide resin, preferably of the polyamide or polylactam type, 80 to 50 parts by weight of rubber, crosslinked to a range corresponding to - a gel gel content of at least 80%; is a homopolymer of 1,3-butadiene, - a copolymer of - 1,3-butadiene with styrene, vinylpyridine, acrylonitrile or methacrylonitrile, or mixtures thereof, and optionally 10 to 30% by weight, of a polyamide resin plasticizer, based on the total weight of the composition. 2. Compositions according to claim 1, characterized in that they comprise: - a crosslinked rubber to the extent corresponding to a content of up to - 4% by weight, at - room temperature of the extractable rubber, based on the composition; determined in the same rubber, as in the composition, is greater than 3 x 10 -5 moles per cm ^{3 of} rubber. 3. The composition of claim 2 comprising a crosslinked rubber to an extent that corresponds to a transverse bond density of the rubber of at least 5 x 10 5 moles per cm 3 of rubber. 4. The composition of claim 2 comprising up to about 4% by weight of extractable rubber. 5. The composition of claim 3, wherein the rubber is a 1,3-butadiene-acrylonitrile copolymer. 6. The composition of claim 5, wherein the polyamide resin is a crystalline linear polyamide derived from a dibasic acid and a diamine. 7. A composition according to claim 6 comprising a mixture of 20 to 45 parts by weight of polyamide resin and 80 to 55 parts by weight of rubber. 8. The composition of claim 7, wherein their tensile strength is at least 50% higher than the tensile strength of the composition comprising uncrosslinked rubber. 9. A composition according to claim 5, wherein the polyamide resin is crystalline linear polylactam, preferably polycaprolactam. 10. The composition of claim 4, wherein the rubber is 1,3-butadiene homopolymer. 11. The composition of claim 10, comprising - a mixture of 20-45 parts by weight of a polyamide resin and 80-55 parts by weight of rubber. 12. The composition according to claim 11, wherein their tensile strength is at least 50% higher than the tensile strength of the non-crosslinked rubber composition. 13. The composition of claim 1, wherein the rubber is a self-vulcanizing nitrile rubber. 14. The composition of claim 6, wherein their toughness, expressed as (TS) ² / E ratio, wherein TS is tensile strength and E is the modulus of elasticity, is at least 50% 2 > greater than the toughness of a similar composition without a resin softener but wherein the weight of the resin exceeds the weight of the rubber and wherein the rubber is crosslinked to the same or greater extent.