JPH0136502B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to surface treatment of inorganic fillers with modified low molecular weight diene polymers. Carbon black has long been used in large quantities as a reinforcing filler in the rubber and plastic industries. However, due to the recent severe crude oil supply situation, there are many concerns about the future of carbon black in terms of price and quantity. Furthermore, carbon black cannot be used as a filler for white or light-colored products because of its black color, and it is also unfavorable in terms of the working environment. Among white fillers, fine powdered silica, known as white carbon, has excellent reinforcing properties in terms of mechanical properties such as modulus and strength. This also causes problems such as a large set of vulcanizate. On the other hand, although calcium carbonate is a relatively inexpensive filler that can be produced in large quantities domestically, its use is limited due to its low reinforcing properties.
It is often used as a bulking agent rather than as a reinforcing agent. Conventionally, the surface of calcium carbonate has been treated with fatty acids or resin acids in order to improve its reinforcing properties, but the reinforcing properties are not always fully satisfactory. do not have. In addition, attempts have been made to obtain calcium carbonate with a high level of reinforcing properties by using an organic polymer with a specific structure as a surface treatment agent for calcium carbonate instead of conventional fatty acids and resin acids. JP-A No. 47-32050, No. 51-
No. 101049, No. 51-142052 and No. 51-53-
Although these surface treatment agents have been proposed in Publication No. 147743 and have certain effects, and their reinforcing properties are improved compared to conventional fatty acids and resin acids, the required performance has diversified. These days, when things are getting tougher, their effects are not necessarily sufficient. On the other hand, as disclosed in Japanese Patent Publication No. 55-40623, for example, a technology is proposed that improves the physical properties of rubber by modifying the molecular structure of rubber to increase interaction with white fillers such as calcium carbonate. Although this technique certainly has the advantage of being applicable to white fillers other than calcium carbonate from the perspective of modified rubber, on the other hand, it also has the advantage of being applicable to white fillers other than calcium carbonate, which is a filler. Apparently, it had the disadvantage that it could only be applied to modified rubber. The present inventors have proposed a molecular weight compound containing 2 to 40 mol% of carboxyl groups based on the monomers constituting the main chain.
A low molecular weight diene polymer having a molecular weight of 1,000 to 120,000, in which 5 to 90% of the carboxyl groups form an amide bond with a primary amine or a secondary amine, which may have a nitrogen atom in the form of a tertiary amine. Do you know it,
Alternatively, the reinforcing properties can be significantly improved by surface treating an inorganic filler such as calcium carbonate with a modified low molecular weight diene polymer that forms an ester bond with an alkanol having a nitrogen atom in the form of a tertiary amine. We have discovered that this and that such surface-treated inorganic fillers are extremely effective in reinforcing rubber, and have arrived at the present invention. That is, according to the present invention, a surface treatment agent for an inorganic filler made of the modified low molecular weight diene polymer, an inorganic filler surface treated with the modified low molecular weight diene polymer, and the surface treated inorganic filler. A rubber composition containing the agent is provided. In the present invention, the low molecular weight diene polymer is
It is a polymer containing a conjugated diene such as butadiene, isoprene, 1,3-pentadiene, etc. as a monomer component, and an unsaturated compound that can be copolymerized therewith as a comonomer component. Coordination anionic polymerization, anionic polymerization,
It can be obtained by polymerization by means such as radical polymerization or by depolymerizing solid rubber such as natural rubber. If the molecular weight of such a low molecular weight diene polymer is too small, even if it is used for surface treatment of the inorganic filler, the effect of improving the reinforcing properties of the treated inorganic filler will be small, and if the molecular weight is too large, the viscosity will be high. Not only does the reaction for modification become difficult, but even when the modified material is used for surface treatment of inorganic fillers, the working efficiency decreases, and as a result, it is difficult to improve the reinforcing properties of the resulting surface-treated inorganic fillers. effectiveness decreases. Therefore, the molecular weight of the low molecular weight diene polymer is preferably in the range of 1,000 to 120,000, particularly 3,000 to 80,000. In addition, if the amount of vinyl bonds in the low molecular weight diene polymer is too large, thickening and gelation are likely to occur during the modification reaction, which not only makes the modification reaction itself complicated, but also makes the resulting modified low molecular weight diene polymer more likely to thicken and gel. When the system polymer is subjected to surface treatment of an inorganic filler, the treatment efficiency also decreases. Therefore, the vinyl bond content of low molecular weight diene polymers is 35% or less,
In particular, it is preferably 25% or less. In addition, in order to suppress thickening and gelation during the modification reaction, it is necessary to pay careful attention to the composition of the low molecular weight diene polymer. For example, when using butadiene or 1,3-pentadiene, the microstructure that makes it difficult to gel It is desirable to select a polymer having . In the present invention, a low molecular weight diene polymer having 2 to 40 mol% of carboxyl groups based on the monomers constituting the main chain refers to the hydrogen atoms on the main chain carbon atoms of the above-mentioned ordinary diene polymers. A monomer having a structure in which some of the atoms are directly substituted with a carboxyl group or substituted with a carboxyl group via an alkylene group having 1 to 5 carbon atoms, and which is polymerized to form a main chain. It refers to a carboxyl group content of 2 to 40 mol%, preferably 5 to 25 mol%, based on the mer components. Here, the term carboxyl group includes acid anhydride groups, and the content is expressed in terms of one acid anhydride group to two carboxyl groups. If the molecular weight of the polymer is too small, the effect of improving the reinforcing properties of the inorganic filler will be poor, and if the molecular weight is too large, the working efficiency for surface treatment of the inorganic filler will decrease, and as a result, the reinforcing properties of the filler will be improved. effectiveness decreases. In the present invention, what is particularly important for improving the reinforcing properties of the inorganic filler is 5 to 90%, preferably 10 to 70%, of the carboxyl groups contained in the above-mentioned low molecular weight diene polymer having carboxyl groups.
is forming an amide bond with a primary amine or secondary amine which may have a tertiary amine nitrogen, or forming an ester bond with an alkanol having a tertiary amine nitrogen. It is practical to form such a bond by reacting a carboxyl group with an amine or an alcohol, but as long as a diene polymer having the bond is obtained as a result, the means for forming the bond can be used in the present invention. Not particularly limited. Also, the amide bond is the first
It also includes an imide bond in which an amine forms an amide bond with two carboxyl groups at the same time. In the present invention, primary amines and secondary amines which may have a nitrogen atom in the form of tertiary amines can be mentioned as suitable amines according to the following general formulas (1), (2),
Shown by (3) and (4). In the above formulas (1), (2), (3) and (4), A ¹ and
A ² is a hydrocarbon chain having 1 to 12 carbon atoms, preferably 1 to 8 carbon atoms, whose carbon-carbon chain may be interrupted by an oxygen atom, and particularly preferably an alkylene group having 1 to 6 carbon atoms, and R ¹ and R ⁶ represents a hydrocarbon group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, particularly preferably an alkyl group having 1 to 6 carbon atoms, and R ² , R ³ , R ⁴
and R ⁵ and R ⁷ and R ⁸ are the same or different from each other,
Each represents a hydrocarbon group having 1 to 12 carbon atoms, preferably 1 to 8 carbon atoms, particularly preferably an alkyl group having 1 to 6 carbon atoms, or together with the nitrogen atom to which they are bonded, a piperidino group, piperazino represents a member of a group, a morpholino group, or a pyrrolidino group. Among these amines, the formula
Rather than the primary amines and secondary amines represented by (1) and (3), the primary amines and secondary amines having nitrogen atoms in the form of tertiary amines represented by formulas (2) and (4), It is more preferred in terms of improving the reinforcing properties of the inorganic filler. The amines used in the present invention are illustrated below. (dimethylamino)ethylamine, (diethylamino)ethylamine, (dimethylamino)propylamine, (diethylamino)propylamine,
(di-i-propylamino)propylamine, (dibutylamino)propylamine, (dimethylamino)ethoxyethylamine, pyrrolidinoethylamine, pyrrolidinopropylamine, piperidinoethylamine, piperidinopropylamine, morpholinoethylamine, morpholinopropyl amine,
Diethylamine, diisopropylamine, dibutylamine, ethylamine, butylamine, propylamine. Preferred alkanols containing nitrogen atoms in the form of tertiary amines in the present invention are those represented by the following general formula (5). In formula (5), R ⁹ and R ¹⁰ are the same or different and each represents a hydrocarbon group having 1 to 15 carbon atoms, preferably 1 to 10 carbon atoms, particularly preferably an alkyl group having 1 to 6 carbon atoms, or they are bonded together. It represents a member of a piperidino, piperazino, morpholino or pyrrolidino group together with a nitrogen atom, and n represents a number from 1 to 20, preferably from 1 to 6. Examples of alkanols that can be used in the present invention include the following. (dimethylamino)ethyl alcohol, (diethylamino)ethyl alcohol, (dimethylamino)propyl alcohol, (diethylamino)propyl alcohol, pyrrolidinoethyl alcohol, pyrrolidinopropyl alcohol, piperidinoethyl alcohol, piperidinopropyl alcohol, morpholinoethyl Alcohol, morpholinopropyl alcohol, 1,3-bis(dimethylamino)-2-hydroxypropane. As mentioned above, as long as a low molecular weight diene polymer containing a predetermined amount of amide bonds or ester bonds in the form of reaction between the above amines or alkanols and carboxyl groups is obtained,
The manufacturing method is not particularly important, but a typical manufacturing method will be explained as follows. A low molecular weight diene polymer having a carboxyl group can be prepared by adding maleic anhydride, maleic acid, maleic acid monoester, thioglycolic acid, etc. in a conventional manner to polybutadiene, polyisoprene, polypentadiene, isoprene-butadiene copolymer, isoprene, etc. -Styrene copolymer, isoprene-acrylonitrile copolymer, isoprene-pentadiene copolymer, butadiene-styrene copolymer, butadiene-acrylonitrile copolymer, isobutylene-isoprene copolymer or ethylene-propylene-diene copolymer, etc. is prepared by addition to a low molecular weight polymer. Additionally, conjugated diene monomers such as butadiene, isoprene or 1,3-pentadiene and monomers having a carboxyl group such as acrylic acid, methacrylic acid or maleic anhydride, i.e. α,β-unsaturated mono- or dicarboxylic acid monomers, can be used. It can also be produced by copolymerizing with a polymer. The content of carboxyl groups can be easily adjusted by adjusting the amounts of reaction components and/or reaction conditions. The modified low molecular weight polymer of the present invention can be obtained by reacting the obtained carboxyl group-containing low molecular weight diene polymer with the above-mentioned primary amine, secondary amine or alkanol. Although the reaction may be carried out at room temperature, it is generally carried out at a temperature of 40 to 220°C. If necessary, organic solvents such as hexane, benzene, toluene, xylene, etc. are used. Low molecular weight diene polymer with maleic anhydride added and general formula (1) or (3)
When the primary amine represented by is reacted, an amide carboxylic acid structure is obtained. However, when the amide carboxylic acid formed by the primary amine is further treated at a high temperature and undergoes a dehydration reaction, it is ring-closed and converted into an imide ring. When reacting a carboxyl group added to a low molecular weight diene polymer with a primary or secondary amine, if the temperature is relatively low and mild, the bonding force between the acid and the amine is due to ionic bonding. weak and easily hydrolyzed. Therefore, in this reaction, it is necessary to carry out the reaction at a relatively high temperature, for example, to sufficiently cause a dehydration reaction between the acid and the amine to form the desired amide structure. It is practical to control the amount of amide or ester bonds formed by the amount of primary amine, secondary amine or alkanol to be reacted. As a method for producing a modified low molecular weight diene polymer, a primary amine or a secondary amine which may have a nitrogen atom in the form of a tertiary amine and α,β-
An amidation product with an unsaturated carboxylic acid or an esterification product between an alkanol having a nitrogen atom in the form of a tertiary amine and an α,β-unsaturated carboxylic acid is directly added to a low molecular weight diene polymer. There is a way. At that time, if it is necessary to also add a compound having a carboxyl group, or if it is better to add a compound having a carboxyl group, in addition to the above amidation product or esterification product, acrylic acid , methacrylic acid, maleic anhydride, maleic acid, or a maleic acid monoester. The amidation product is a product obtained by amidation of an amine represented by the general formulas (1) to (4) with an α,β-unsaturated carboxylic acid such as acrylic acid, methacrylic acid, maleic anhydride or maleic acid. Examples of reaction products that are preferably used include (meth)acrylamides such as N,N-dimethylaminopropylmethacrylamide or N,N-diethylaminopropylmethacrylamide, N-dimethylmaleamic acid, and N-diethylmaleaamide. acid, N(N',N'-dimethylamino)ethylmaleamic acid, N(N',N'-dimethylamino)propylmaleamic acid, N(N',N'-diethylamino)ethylmaleamic acid or N (N′,
Maleamic acids such as N'-diisopropylamino)ethylmaleamic acid, or N(N',N'-dimethylamino)ethylmaleimide, N(N',N'-diethylamino)ethylmaleimide, N(N',N' -diisopropylamino)ethylmaleimide, N
Examples include (N',N'-dimethylamino)propylmaleimide and N(N',N'-diethylamino)propylmaleimide. The esterification product is a reaction product of the alkanol represented by the general formula (5) and acrylic acid, methacrylic acid, maleic anhydride, or maleic acid, such as N,N-dimethyl Aminoethyl acrylate, N,N-diethylaminoethyl acrylate, N,N-dimethylaminopropyl acrylate, N,N-diethylaminopropyl acrylate, N,N-dimethylaminoethyl methacrylate, N,N-dimethylaminopropyl methacrylate or N,N -(meth)acrylates such as -dimethylamino-2-hydroxypropyl methacrylate. these,
Among the amidation or esterification products of unsaturated carboxylic acids which may have a nitrogen atom in the form of a tertiary amine, maleamic acid or maleimide which has a nitrogen atom in the form of a tertiary amine; is preferably used. The addition reaction of these amidation products or esterification products to a low molecular weight diene polymer can be carried out in the same manner as the addition reaction of an unsaturated carboxylic acid or its derivative to a low molecular weight diene polymer. The addition reaction is carried out by heating the reaction at 60 to 230°C, with or without using a solvent or a radical catalyst. Anti-gelling agents are sometimes used during the reaction, but in order to suppress thickening and gelling during the reaction, isoprene-based polymers are recommended as the low molecular weight diene-based polymers used in the reaction. Combination is preferred. Also, butadiene, isoprene or 1,3-
By copolymerizing amidation or esterification products of unsaturated carboxylic acids which may have nitrogen atoms in the form of tertiary amines when polymerizing conjugated diene monomers such as pentadiene. Also, a modified low molecular weight diene polymer can be obtained. The amidation product or esterification product of an unsaturated carboxylic acid which may have a nitrogen atom in the form of a tertiary amine used herein may be as described above, but especially in the form of a tertiary amine. (Meth)acryamide or (meth)acrylate having a nitrogen atom is preferably used. In the copolymerization, an α,β-unsaturated carboxylic acid may be used as a copolymerization component, if necessary. In such copolymerization, a radical polymerization method is preferable in view of the difficulty in controlling the amount of the monomer component introduced since the monomer component has a functional group. The modified low molecular weight diene polymer thus obtained can improve the reinforcing properties of inorganic fillers such as calcium carbonate, magnesium carbonate, zinc carbonate, clay, kerk, silica, mica, barium sulfate, calcium sulfate or aluminum sulfate. extremely useful. The treatment of an inorganic filler using the polymer and the incorporation of the treated filler into solid rubber will be described below. The modified low molecular weight diene polymer may be used for surface treatment of the inorganic filler as it is or in a state dissolved or dispersed in water, an organic solvent, or a mixed solvent of organic solvent/water. From the viewpoint of treatment efficiency, it is preferable that some or all of the carboxyl groups and acid anhydride groups contained in the modified low molecular weight diene polymer are neutralized with a basic compound. Here, the basic compound is a compound that can neutralize and form an ionic bond with a carboxylic acid in a low molecular weight diene polymer. Examples include monovalent amines such as hydroxides of alkali metals, ammonia, dialkylamines, and n-butylamine. This neutralization reaction can be carried out in an aqueous medium, in an organic solvent medium, or in a water/
It is carried out in a mixed organic solvent. Examples of organic solvents used here include butyl acetate, ethylene glycol monomethyl ether acetate, ethylene glycol monoether acetate-3-methoxybutanol, ethylene glycol monomethyl ether,
Mention may be made of dioxane, methyl isopropyl ketone, methyl ethyl ketone, acetone, xylene or toluene. Since the use of organic solvents may cause problems in post-treatment, treatment in an aqueous medium is most preferred. In this case, from the viewpoint of dispersibility in water, it is desirable that the modified low molecular weight diene polymer before the neutralization reaction contains 8 mol % or more of carboxyl groups. The neutralization reaction does not necessarily need to be carried out on all of the added carboxyl groups or acid anhydride groups, but in terms of carboxyl groups (one acid anhydride group is calculated as two carboxyl groups),
It is preferable to neutralize at least 10%, more preferably 50% or more. Modified low molecular weight diene polymers can be applied to a wide range of inorganic fillers as mentioned above, but they give particularly favorable results when used for surface treatment of calcium carbonate. will be explained below. In general, calcium carbonate with a small particle size is used, for example, in "Practical Handbook of Additives for Plastics and Rubber" (Kagaku Kogyosha, published August 10, 1970), No. 589.
As described in the page, water is added to quicklime obtained by calcining limestone to make a calcium hydroxide slurry, and by contacting the slurry with carbon dioxide gas, it is precipitated as fine particles of calcium carbonate. However, the modified low molecular weight diene polymer can be added immediately before, simultaneously with, or immediately after blowing in carbon dioxide gas. good. Depending on the case, a method may be used in which the blowing of carbon dioxide gas and the addition of the modified low molecular weight diene rubber are alternately repeated several times. As a typical example, after carbon dioxide gas is blown into the calcium hydroxide slurry, a modified low molecular weight diene polymer is added, and after thorough stirring and mixing, carbon dioxide gas is further blown into the slurry, followed by the next dehydration process. Examples include a method of subjecting the material to a drying process. At this time, the modified low molecular weight diene polymer should be added in the form of a solution or dispersion using an organic solvent or a mixed solvent of organic solvent/water, from the viewpoint of surface treatment efficiency and wastewater post-treatment. It is more preferable to add it in the form of an aqueous solution or aqueous dispersion. In addition, when surface treating calcium carbonate with a low molecular weight diene polymer, fatty acids and resin acids, which have traditionally been used as surface treatment agents, as well as various surfactants, lignin,
Water-soluble polymers such as silane compounds, organic titanates, polyacrylic acids, and carboxymethyl cellulose, low molecular weight diene polymers that have only carboxyl groups as functional groups, and low molecular weight diene polymers that have only amino groups as functional groups. may be used together. Such surface treatment can also be applied to magnesium carbonate and other inorganic fillers. The surface-treated inorganic filler made of the modified low molecular weight diene polymer obtained in this way generally has an average
It has a particle size of 0.001 to 50μ. If the powder becomes extremely fine, it may cause problems in handling as a filler, and if the particle size is large, the reinforcing properties will be reduced, so the particle size of calcium carbonate or magnesium carbonate should be 0.005 to 5μ. is more preferable. The same applies to other inorganic fillers. The modified low molecular weight diene polymer is generally applied in an amount of 0.05 to 20 parts by weight per 100 parts by weight of the inorganic filler.
If the amount of modified low molecular weight diene polymer attached is too small, the reinforcing effect of the inorganic filler will be reduced, while if the amount attached is too large, it will be difficult to obtain uniform fine particles of calcium carbonate. This not only causes problems in physical properties, but also increases the cost of the inorganic filler, reducing its significance as an industrial technology. Taking these into consideration, the amount of the modified low molecular weight diene polymer attached is preferably in the range of 0.5 to 10 parts by weight per 100 parts by weight of the inorganic filler. Such inorganic fillers surface-treated with modified low molecular weight diene polymers, especially calcium carbonate or magnesium carbonate, can be used for natural rubber, synthetic polyisoprene rubber, polybutadiene rubber, polypentadiene rubber, isoprene-butadiene copolymer rubber, Diene rubbers such as styrene-diene (butadiene or isoprene) copolymer rubber, acrylonitrile-diene (butadiene or isoprene) copolymer rubber, chloroprene rubber, ethylene-propylene-diene copolymer rubber, or mixtures thereof, ethylene-acrylic copolymer When used as a reinforcing filler in ethylene rubbers such as polymers, ethylene-vinyl acetate copolymers, ethylene-propylene copolymers, etc., or mixtures thereof, a great reinforcing effect is brought about. Of course, polyurethane rubber,
It goes without saying that the present invention can also be applied to other rubbers such as silicone rubber, fluorocarbon rubber, polyester rubber, and epichlorohydrin rubber. In the case of rubber compounding, in addition to the inorganic filler whose surface is treated with modified low molecular weight diene rubber, vulcanizing agents such as sulfur, peroxide or quinone oxime, vulcanization accelerators, stearic acid, zinc oxide, and anti-aging agents are used. , rubber compounding chemicals such as plasticizers are added as appropriate. Also, untreated fillers (eg, carbon black, silica, clay, mica) or conventional surface-treated fillers may be added, if desired. In such rubber formulations, inorganic fillers surface-treated with modified low-molecular-weight diene polymers, especially calcium carbonate and magnesium carbonate, are usually added in an amount of 5 to 500 parts by weight per 100 parts by weight of the rubber, etc. to exert reinforcing properties, etc. If you consider
It is used in a proportion of 20 to 300 parts by weight. The rubber compound thus obtained is mixed in a kneader, roll mill, Banbury mixer, extruder, etc., and vulcanized and molded to produce rubber products such as tires, belts, rubber rolls, anti-vibration materials, rubber hoses, various industrial products, and even footwear. Used in products. EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited to these Examples in any way. Example 1 and Comparative Examples 1 and 2 By reacting maleic anhydride (hereinafter abbreviated as MAN) at 180°C with low molecular weight polyisoprene having a number average molecular weight of 13,000 and a vinyl bond content of 100%, MAN was A low molecular weight polyisoprene (LMP-A) with 18 mol% addition was obtained. The amount of MAN added to this MAN-modified low molecular weight polyisoprene was determined by measuring the acid value using a suitable method.
Next, (diethylamino)ethylamine was added in an equimolar amount to the added MAN, and the mixture was reacted at 100°C. When the infrared spectrum of the reaction product was measured, the absorption around 1790 and 1865 cm ^-1 based on the acid anhydride groups that existed before the addition of the amine completely disappeared after the addition and reaction of the amine, and new
Absorption based on amide carboxylic acid appeared at 1700 cm ^-1 , confirming that almost 100% of the amine had reacted. That is, by reacting the above amine, a modified low molecular weight polyisoprene (LMP-B) to which 18 mol% of N(N',N'-diethylamino)ethylmaleamic acid (hereinafter abbreviated as MA) was added was obtained. It was found that Next, the aforementioned N(N',N'-diethylamino)ethylmaleamic acid-modified low molecular weight polyisoprene was dissolved in an aqueous sodium hydroxide solution and completely neutralized to prepare a 10% by weight aqueous solution. Carbon dioxide gas is inhaled into a 15% by weight calcium hydroxide slurry prepared by adding water to quicklime, and at the same time the formation of calcium carbonate begins, the above N
A sodium hydroxide aqueous solution of (N',N'-diethylamino)ethylmaleamic acid-modified low molecular weight polyisoprene was added to 100 parts by weight of calcium carbonate so that the solid content of the modified low molecular weight polyisoprene was 5 parts by weight. , the pH of the mixed liquid is 9.0 under stirring.
Continue blowing in carbon dioxide until The aqueous dispersion of calcium carbonate is then dehydrated and dried to reduce the particle size.
Surface-treated calcium carbonate with MA-modified low molecular weight polyisoprene of 0.04-0.1μ was obtained. In addition, when the water dehydrated from the calcium carbonate aqueous dispersion was analyzed, it was found that approximately 8% by weight of the added amount was contained in the dehydrated water.
of modified low molecular weight polyisoprene was detected, and approximately 92% by weight of the added amount was consumed on the surface of calcium carbonate,
It was found that it was added. Calcium carbonate surface-treated with N(N',N'-diethylamino)ethylmaleamidic acid-modified low molecular weight polyisoprene was roll-mixed according to the synthetic cis-1,4-polyisoprene rubber formulation shown in Table 1. The physical properties of the obtained vulcanized rubber were examined based on JIS. The results are shown in Table 2.

[Table] On the other hand, for comparison, MAN-modified low-molecular-weight polyisoprene was treated in the same manner as above, except that calcium carbonate was surface-treated with an aqueous sodium hydroxide solution, and calcium carbonate was surface-treated with a commercially available fatty acid. When sulfur rubber was produced, the results shown in Table 2 were obtained. Note that calcium carbonate surface-treated with a sodium hydroxide aqueous solution of MAN-modified low-molecular-weight polyisoprene is
MAN modified low molecular weight polyisoprene (LMP-A)
was made into an aqueous sodium hydroxide solution in the same manner as in the above method, and was prepared by surface treatment in the same manner as in the above method. The amount of MAN-modified low-molecular-weight polyisoprene added to calcium carbonate was about 92% by weight, similar to the amount of MA-modified low-molecular-weight polyisoprene. In addition, the particle size of calcium carbonate is the same as above.
It was 0.04 to 0.1μ.

[Table] As is clear from Table 2, calcium carbonate surface-treated with N(N',N'-diethylamino)ethylmaleamide-modified low molecular weight polyisoprene
Shows significantly superior reinforcing properties compared to those surface-treated with MAN-modified low molecular weight polyisoprene. In particular, the improvement in the 300% modulus, hardness, and tear strength of vulcanized rubber is remarkable. Example 2 and Comparative Example 3 MAN was produced by reacting maleic anhydride (MAN) with low molecular weight polyisoprene having a number average molecular weight of 5500 and a vinyl bond content of 62% at 200°C.
A modified low molecular weight polyisoprene (LMP-C) with 13 mol% addition was obtained. Next, dibutylamine is added to this MAN-modified low molecular weight polyisoprene.
By adding 0.7 molar equivalent of MAN and heating and stirring at 80°C, a part of the added MAN is reacted with the amine, and finally MAN is 3.9 mol% and N-dibutyl maleamic acid (abbreviated as MA). Modified low molecular weight polyisoprene with 9.1 mol% added (LMP-D)
I got it. The MAN-modified low molecular weight polyisoprene (LMP-C) and MA-modified low molecular weight polyisoprene (LMP-D) were each dissolved in an aqueous potassium hydroxide solution and completely neutralized to prepare a 10% by weight aqueous solution. Carbon dioxide gas is sufficiently blown into a 15% by weight calcium hydroxide slurry prepared by adding quicklime to water to precipitate calcium carbonate.
After adding an aqueous potassium hydroxide solution of MAN-modified low molecular weight polyisoprene and an aqueous potassium hydroxide solution of MA-modified low molecular weight polyisoprene in amounts corresponding to 3.5 parts by weight of solids per 100 parts by weight, and stirring vigorously, It was dehydrated and dried to obtain low molecular weight polyisoprene surface-treated calcium carbonate having a particle size of 0.05 to 0.09μ. When the water produced during the above dehydration was analyzed, it was found that about 80% by weight of the added amount of modified low molecular weight polyisoprene was attached to the calcium carbonate. A compound of synthetic cis-1,4-polyisoprene rubber was prepared according to the formulation shown in Table 1 in Example 1, and was vulcanized in the same manner as in Example 1, and the physical properties of the vulcanization were measured (Table 3). ), the contribution of the vulcanization properties of surface-treated calcium carbonate to the effectiveness was investigated.

[Table] <Vulcanized physical properties>
300% modulus (Kg〓cm ² ) 31 21
Breaking strength (〃) 249 213
Elongation at break (%) 740 770
Hardness 〓JIS-A〓 54 49

Claims (1)

[Claims] 1. 2 to 40 mol% based on the monomers constituting the main chain
Molecular weight 1000-120000 containing carboxyl group
A low molecular weight diene polymer, in which 5 to 90% of the carboxyl groups form an amide bond with a primary amine or secondary amine, which may have a nitrogen atom in the form of a tertiary amine. , or a surface treatment agent for an inorganic filler comprising a modified low molecular weight diene polymer forming an ester bond with an alkanol having a nitrogen atom in the form of a tertiary amine. 2 2 to 40 mol% based on the monomers constituting the main chain
Molecular weight 1000-120000 containing carboxyl group
A low molecular weight diene polymer, in which 5 to 90% of the carboxyl groups form an amide bond with a primary amine or secondary amine, which may have a nitrogen atom in the form of a tertiary amine. , or an inorganic filler surface-treated with a modified low molecular weight diene polymer forming an ester bond with an alkanol having a nitrogen atom in the form of a tertiary amine. 3 2 to 40 mol% based on the monomers constituting the main chain
Molecular weight 1000-120000 containing carboxyl group
A low molecular weight diene polymer, in which 5 to 90% of the carboxyl groups form an amide bond with a primary amine or secondary amine, which may have a nitrogen atom in the form of a tertiary amine. or a rubber composition containing an inorganic filler surface-treated with a modified low molecular weight diene polymer forming an ester bond with an alkanol having a nitrogen atom in the form of a tertiary amine.