JPH0240691B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a rubber composition, and more specifically to a rubber composition having excellent processability and physical properties of vulcanized rubber by blending a specific blocked polyisocyanate and a compound having active hydrogen into solid rubber. Regarding providing. Conventionally, in the processing of solid rubber, process oil and various plasticizers have been added to improve processability. However, although these process oils and plasticizers are effective in improving processability, they exist as foreign substances in the resulting vulcanized rubber, causing deterioration in the physical properties of the vulcanized rubber. Therefore, in recent years, attempts have been made to add butadiene-based and isoprene-based low-molecular oligomers to improve this, but they have not been able to achieve sufficient effects. Furthermore, it has been proposed to add a liquid polybutadiene having a hydroxyl group at the end or a prepolymer obtained from this liquid polybutadiene and an excess of diisocyanate (Japanese Patent Publication No. 19333/1982 and Japanese Patent Publication No. 26976/1989). However, simply adding the above-mentioned liquid polybutadiene does not produce a satisfactory effect, while using a prepolymer obtained from liquid polybutadiene and diisocyanate is not effective in improving the physical properties of vulcanized rubber. Although it is recognized that there is a problem, there is a drawback that the processability is extremely poor due to the urethane reaction that occurs during rubber processing. The present inventors have conducted extensive research in order to eliminate these drawbacks and develop a rubber composition that has excellent processability and vulcanized rubber physical properties. As a result, solid rubber added with a specific blocked polyisocyanate and an active hydrogen group-containing compound is easy to process due to its low viscosity during processing such as kneading, and is also suitable for vulcanized rubber products. It has been found that if a heating treatment is performed after this process, the blocks dissociate and the reactivity of the polyisocyanate increases, resulting in a vulcanized rubber product with excellent physical properties. The present invention was completed based on this knowledge. That is, the present invention provides a rubber composition comprising (A) a solid rubber, (B) a blocked polyisocyanate containing a polydiene chain, and (C) an active hydrogen group-containing compound. The solid rubber that is component (A) used in the present invention is a base component of the composition of the present invention, and various types can be used depending on the purpose of use. Specific examples include natural rubber, styrene-butadiene rubber, butadiene rubber, acrylonitrile-butadiene rubber, chloroprene rubber, isoprene rubber, ethylene-propylene rubber, ethylene-propylene-diene rubber, and mixtures thereof. Next, the blocked product of polydiene chain-containing polyisocyanate, which is component (B) of the composition of the present invention, is as follows:
It has a structure in which a blocking agent for masking the isocyanate groups is bonded to the isocyanate group of a polyisocyanate containing a polydiene chain (urethane prepolymer containing an isocyanate group containing a polydiene chain in the molecular chain). Here, the above polydiene chain-containing polyisocyanate is produced by reacting an organic polyisocyanate compound with a liquid diene polymer having an active hydrogen group such as a hydroxyl group, an amino group, an imino group, a carboxyl group, or a mercapto group at the molecular end. This is a urethane prepolymer obtained by As the liquid diene polymer, a diene polymer having a number average molecular weight of 500 to 25,000 and having 4 to 12 carbon atoms,
There are copolymers thereof, and copolymers of these diene monomers and α-olefinic addition polymerizable monomers having 2 to 22 carbon atoms. Of course, the term also includes liquid diene polymers modified by adding unsaturated carboxylic acids such as maleic anhydride or derivatives thereof to these liquid diene polymers. Specific examples include butadiene homopolymer, isoprene homopolymer, butadiene-styrene copolymer, butadiene-isoprene copolymer, butadiene-acrylonitrile copolymer, butadiene-2-ethylhexyl acrylate copolymer, butadiene-n-octadecyl acrylate copolymer, etc. . Among them, the viscosity is 2000 poise or less, more preferably 500 poise or less, and the chemical structure is 1 to 4.
It is preferred to use (co)polymers with a bond of 50% or more. On the other hand, examples of organic polyisocyanate compounds that react with the liquid diene polymer include tolylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, polyethylene polyphenyl polyisocyanate, liquid modified diphenylmethane diisocyanate, xylylene diisocyanate, and cyclohexane diisocyanate. Nylene diisocyanate, cyclohexyl diisocyanate, naphthalene-1,5-diisocyanate, xylylene-2,2'-diisocyanate, isopropylbenzene-2,4-diisocyanate, addition reaction product of polypropylene glycol and tolylene diisocyanate, 1 mole of trimethylolpropane and tolylene diisocyanate Examples include addition reaction products with 3 moles of isocyanate. In order to produce the above-mentioned polydiene chain-containing polyisocyanate, it is sufficient to react the above-mentioned liquid diene-based polymer with an organic polyisocyanate compound.
The reaction conditions at this time are not particularly limited and may be appropriately selected. For example, the reaction temperature may be 30 to 100° C. and the reaction time may be in the range of 10 minutes to 10 hours under an inert gas flow such as dry nitrogen. In addition, in the above reaction,
Active hydrogen group-containing compounds other than the above-mentioned liquid diene polymers can also be used in combination. Component (B) of the present invention is a polyisocyanate containing a polydiene chain obtained by the above method, in which a blocking agent for masking the isocyanate groups is bound to the isocyanate groups. Here, blocking agents include phenols such as phenol, cresol, xylenol, and nonylphenol, alcohols such as methanol, ethanol, and isopropanol, lactams such as caprolactam and butyrolactam, and oximes such as acetoxime, methyl ethyl ketoxime, and cyclohexanoxime. , other imides, esters, etc. Furthermore, component (C) in the composition of the present invention is a compound containing an active hydrogen group, and specifically includes the above-mentioned liquid diene polymer having an active hydrogen group and other compounds. Here, the liquid diene polymer is as described above, but other active hydrogen group-containing compounds include ethylene glycol, propylene glycol, 1,4-butanediol, glycerin,
Low molecular weight polyols such as trimethylolpropane, 1,2,6-hexanetriol, pentaerythritol, ethylenediamine, 4,4'-methylene-bis-2-chloroaniline, 4,4'-methylene-bis-2-ethylaniline and polyether polyols such as propylene oxide adducts of bisphenol A, which are obtained by addition polymerizing alkylene oxides such as ethylene oxide and propylene oxide to low-molecular polyols or amine compounds.
Furthermore, even if it is a condensation polymer of polyhydric alcohols such as ethylene glycol, propylene glycol, and 1,4-butanediol, and polybasic acids such as phthalic acid, maleic acid, malonic acid, succinic acid, adipic acid, and terephthalic acid, Polyester polyols having hydroxyl groups at the ends, acrylic polyols, coconut oil, tall oil, etc. can also be mentioned. The blending ratio of the above components (A), (B), and (C) in the composition of the present invention is not particularly limited and may be determined depending on various conditions, but usually the solid rubber that is component (A)
A total of 1 to 50 parts by weight, preferably 2 to 30 parts by weight of components (B) and (C) are blended to 100 parts by weight, and
It is preferable that the ratio of component (B) and component (C) is such that the isocyanate group in component (B) and the active hydrogen group in component (C) are 0.8 to 1.2 (equivalent ratio). In the composition of the present invention, even if components (A), (B), and (C) are blended, since the isocyanate group in component (B) is blocked, (A), (B), ( C) no reaction occurs between the components. Therefore, processability and stability are good when kneading these components. Moreover, since the components (B) and (C), especially the component (B) in the composition of the present invention act as a processing aid or plasticizer during processing, the processability becomes even better. The composition of the present invention basically consists of the above three components (A), (B), and (C), but may further contain sulfur, a vulcanizing agent such as magnesium oxide, zinc oxide, Vulcanization aids such as stearic acid, vulcanization accelerators such as mercaptobenzothiazole, dibenzothiazyl disulfide, N-cyclohexyl-2-benzothiazyl sulfinamide, plasticizers, processing aids such as process oil, Alternatively, an appropriate amount of filler (reinforcing agent) such as carbon black, white carbon, or pigment can be added. The composition of the present invention can be obtained by thoroughly kneading the above components (A), (B), and (C) and various additives as necessary, but the processing temperature at this time is usually It should be controlled below 100℃. If the temperature is too high, the blocking agent will dissociate from the blocked isocyanate groups in component (B), which may cause vulcanization reactions to proceed during kneading. The composition of the present invention does not react during kneading processing, and since component (B) acts as a processing aid, plasticizer, etc., the viscosity is relatively low even without the addition of other processing aids, and the composition is easy to process. is very good. Moreover,
It is stable because it does not react, and the storage stability of unvulcanized rubber is excellent. Further, the composition of the present invention can be processed at temperatures above 100°C, preferably from 120 to 160°C, after being processed into products.
When heated to a temperature of approximately It will be excellent. On this occasion,
Component (B) is an activated isocyanate group that reacts with the active hydrogen group-containing compound (C) and other additives or the solid rubber (A) to improve the physical properties of the product. contribute greatly to As mentioned above, the composition of the present invention is not only easy to process, but also provides excellent physical properties when vulcanized into a product. Therefore, the composition of the present invention can be effectively used in the production of various rubber products. Next, the present invention will be explained in more detail with reference to Examples. Examples and Comparative Examples Compounding and kneading were carried out using the compounding ratios shown in Table 1 and in accordance with the preparation specifications for rubber compounding agents below. In addition,
The blending of the blocked polydiene chain-containing polyisocyanate, component (B), was the same as when blending the process oil. NR (natural rubber) …ASTM D3184 SBR (styrene-butadiene rubber) …JIS K6383 BR (butadiene rubber) …ASTM D3189 NBR (acrylonitrile-butadiene rubber)
...JIS K6384 CR (chloroprene rubber) ...JIS K6388 Next, the physical properties of the unvulcanized rubber of the obtained composition were measured in accordance with the unvulcanized rubber physical test method of JIS K6300. Further, the product was cured by vulcanization to obtain a vulcanized rubber product, and its normal physical properties were measured in accordance with JIS K6301. Incidentally, the vulcanization time was determined by measuring the 90% curing time.

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Claims (1)

[Scope of Claims] 1. A rubber composition comprising (A) a solid rubber, (B) a blocked polyisocyanate containing a polydiene chain, and (C) an active hydrogen group-containing compound. 2. A total of 1 to 50 parts by weight of (B) a blocked polyisocyanate containing a polydiene chain and (C) an active hydrogen group-containing compound to 100 parts by weight of (A) solid rubber;
and isocyanate group/active hydrogen group is 0.8 to 1.2
The rubber composition according to claim 1, which is blended in a ratio of (equivalent ratio).