JPH10273511A - Flexible elastomer composition and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize the molding at low pressure, control the production cost and improve the productivity by grafting a main polymer comprising mainly a hydrogenated styrene/isoprene/styrene copolymer, etc., with a compound containing an alkoxysilane group, molding the graft polymer, solidifying the molding, subjecting the solidified molding to condensation by using moisture, and then subjecting the condensate to three-dimensional cross-linking. SOLUTION: A hydrogenated styrene/butadiene/styrene copolymer can also be used. 100 pts.wt. main polymer, blended with 300-2,500 pts.wt. plasticizer, is grafted with 0.5-50 pts.wt. compound containing an alkoxysilane group (e.g. vinyltriethoxysilane) by using 0.1-30 pts.wt. organic peroxide (e.g. benzoyl peroxide). The graft polymer is mixed with 0.1-20 pts.wt. silanol condensation catalyst (e.g. dibutyltin dilaurate) in an atmosphere of dry nitrogen at 100-210 deg.C. The mixture is injection molded at low pressure, the molding is subjected to condensation through alcohol removal by using moisture, and the condensate is subjected to three-dimensional cross-linking.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soft elastomer composition containing a softener / plasticizer in excess with respect to a main polymer, having low hardness and excellent heat deformation resistance, and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, as a polymer elastomer composition used in the fields of electronic equipment, leisure goods, daily necessities, etc., as its use has expanded, its hardness and elasticity have been reduced.
High strength is required. As a main polymer of such an elastomer composition, a non-crystalline styrene-based thermoplastic elastomer is very suitable in terms of lowering hardness. In other words, a styrene-based thermoplastic elastomer is
It is extremely excellent in low hardness among thermoplastic resins, has a three-dimensional structure with strong bonding strength, and is a bond selectively plasticized by a plasticizer. Are better.

[0003]

However, when a styrene-based thermoplastic elastomer is used as the main polymer, the heat resistance tends to decrease significantly when a large amount of a plasticizer is blended, causing a problem in practicality. .

As a method for improving heat resistance, for example, as disclosed in Japanese Patent Application Laid-Open No. 7-252397, a method is known in which three-dimensional crosslinking is performed by irradiating an electron beam or an ultraviolet ray in the presence of an initiator. ing. However, this method has a problem that the manufacturing equipment is expensive and the manufacturing cost is increased, and that the manufacturing apparatus must be installed in consideration of the influence on the human body.

On the other hand, Japanese Patent Application Laid-Open No. Hei 5-117149 discloses an elastomer obtained by using a polymer vinyl SIS block copolymer as a main polymer, grafting a silane coupling agent to the copolymer, and then contacting with water to form a three-dimensionally crosslinked elastomer. A composition is disclosed. However, since the polymer vinyl SIS block copolymer used as the main polymer has a low tensile strength, it is very difficult to reduce the hardness by excessively blending a plasticizer or a softener.

The present invention has been made in view of the above problems, and has excellent low-curing properties and flexibility by containing a large amount of a plasticizer and / or a softening agent, and also has excellent heat deformation resistance. It is an object of the present invention to provide a flexible elastomer composition. Another object of the present invention is to easily produce the above-mentioned soft elastomer composition having low hardness and excellent heat resistance.

[0007]

Accordingly, a method for producing a flexible elastomer composition according to the present invention is directed to a hydrogenated styrene-isoprene-styrene copolymer (SEPS) or a hydrogenated styrene-butadiene-styrene copolymer (SPS). SEBS)
After blending an excess plasticizer or / and softening agent with the main polymer containing as a main component, a graft reaction of an alkoxysilane group-containing compound is performed using an organic peroxide, and then injection molding is performed at a low pressure. It is characterized by being solidified by cooling, followed by condensation by dealcoholation using water and three-dimensional crosslinking.

[0008] The soft elastomer composition according to the present invention is produced by the above production method,
30 parts by weight of a plasticizer is added to 100 parts by weight of the main polymer.
0 to 2500 parts by weight, 0.5 to 50 parts by weight of an alkoxysilane group-containing compound, 0.1 to 30 parts by weight of an organic peroxide, and 0.1 to 20 parts by weight of a silanol condensation catalyst. Features.

A main component of the main polymer is a styrene-isoprene-styrene copolymer (SI) having a polystyrene phase at both ends and an intermediate phase comprising polyisoprene.
S) having a styrene-based thermoplastic elastomer of a hydrogenated styrene-isoprene-styrene copolymer (SEPS) having an intermediate phase of an ethylene / propylene block copolymer by hydrogenation, or a polystyrene phase at both ends,
A hydrogenated styrene-butadiene-styrene copolymer (SEB) is obtained by hydrogenating a styrene-butadiene-styrene copolymer (SBS) whose intermediate phase is composed of polybutadiene to make the intermediate phase an ethylene / butylene block copolymer.
The styrene thermoplastic elastomer (S) is used.

The main polymer may be composed of only the above-mentioned SEPS and SEBS.
Of the 00 parts by weight, 0.5 to 20 parts by weight can be contained. By blending SIS or SBS in this way, the gel fraction can be appropriately increased according to the purpose,
Heat resistance and physical properties can be further improved.

As the above-mentioned plasticizer and softener, commonly used well-known plasticizers can be appropriately used. For example, vegetable oil-based softeners, mineral oil-based softeners, synthetic plasticizers, more preferably mineral oil-based softeners , Naphthenic or aroma oils, hydrocarbon oils of synthetic plasticizers, or hydrocarbon oligomers. Such a plasticizer / softening agent is added in excess of 100 parts by weight, more preferably 300 to 2500 parts by weight, based on 100 parts by weight of the main polymer.

The above alkoxysilane group-containing compound can be represented by the general formula X-Si (OR) ₃ . Here, X is a group that can react with an organic substance such as a vinyl group, an epoxy group, a methacryl group, an amino group, and a mercapto group, and R is a hydrolyzable group such as a methoxy group and an ethoxy group. Examples of suitable alkoxysilane group-containing compounds include vinyl group-containing compounds such as vinyltriethoxysilane, vinyltrimethoxysilane, and vinyltriacetoxysilane. The compounding amount of such an alkoxysilane group-containing compound depends on the main polymer 10
0.5 to 50 parts by weight per 0 parts by weight is preferred. When the amount is less than 0.5 part by weight, the three-dimensional crosslinking reaction is not sufficiently performed. On the other hand, when the amount is more than 50 parts by weight, the effect corresponding to the blending amount cannot be obtained.

Examples of the above organic peroxide include benzoyl peroxide, 1,1-bis-t-butylperoxy-3,3,5-tri-methylcyclohexane, 1,1
-Bis (t-butylperoxy) cyclododecane, n-
Butyl-4,4-bis-t-butylperhexylvalerate, dicumyl peroxide, t-butylperoxybenzoate, di-t-butyl peroxide, di- (t
-Butylperoxy) m-diisopropylbenzene,
2,5-dimethyl-2,5-di-t-butylperoxyhexane, 2,5-dimethyl-2,5-t-butylperoxylhexyne-3, t-butylperoxycumin and the like can be mentioned. it can. The amount of the organic peroxide is preferably 0.1 to 30 parts by weight based on 100 parts by weight of the main polymer. If the amount is less than 0.1 part by weight, the desired effect cannot be obtained, and if the amount is more than 30 parts by weight,
The effect corresponding to the added amount cannot be obtained.

Examples of the silanol condensation catalyst include dibutyltin dilaurate (DBTDL), dibutyltin acetate, tributyltin dilaurate (TBTDL), and the like.
0 parts by weight is preferred.

The soft elastomer composition according to the present invention is produced, for example, as follows. 100-210
The plasticizer / softening agent is melted and mixed with the main polymer using a stirrer or the like in air at 0 ° C, in a vacuum, more preferably in a nitrogen atmosphere, and then the alkoxysilane group-containing compound is mixed with stirring. Then, the organic peroxide is stirred and mixed to cause a graft reaction of the alkoxysilane group. After the reaction, reduced pressure is applied to remove the residual of the reaction.

Next, the silanol condensation catalyst is stirred and mixed in a dry nitrogen atmosphere at 100 to 210 ° C., and the pressure is reduced to remove air bubbles and prevent air bubbles from entering the product. Then, the mixture is poured into a mold having a desired shape at a low pressure to perform injection molding, and is solidified by cooling to obtain an intermediate molded product. This intermediate molded product is inferior in heat-resistant deformation because it is not crosslinked as it is. Thus, condensation and three-dimensional cross-linking are performed by dealcoholation using water to improve heat resistance. This condensation and cross-linking step is performed, for example, by immersing in warm water of 50 ° C. or lower, or by exposing it to atmospheric moisture.

[0017]

As described above, according to the present invention, since a styrene-based thermoplastic elastomer such as SEPS or SEBS is used as a main component of the main polymer, a plasticizer / softener, an organic peroxide and an alkoxysilane are used. The group-containing compound can be easily compounded, the compound can be handled as a low-viscosity fluid, and injection molding at a low pressure that can reduce equipment investment becomes possible. In addition, since three-dimensional crosslinking can be performed using water, the manufacturing cost can be reduced as compared with the conventional example in which crosslinking is performed by irradiating an electron beam or ultraviolet light, as described above.
There is no restriction on the installation position, and productivity is significantly improved.

Here, the crosslinking step using water can be carried out at a temperature near room temperature, for example, by exposing to hot water of 50 ° C. or lower, or to exposure to atmospheric moisture. It becomes even easier.

The soft elastomer composition obtained has a sufficient flexibility as a soft elastomer composition, although the modulus tends to increase with an increase in the degree of crosslinking.
It retains low hardness and has excellent heat resistance due to three-dimensional crosslinking.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following Table 1 shows the formulations and various performance test results for the elastomer compositions of Examples 1 to 7 and Comparative Examples 1 and 2.

[0021]

[Table 1]

Example 1 A styrene-based thermoplastic elastomer (having a molecular weight of about 10
100 parts by weight of SEBS (Clayton G1650; manufactured by Shell Petrochemicals Co., Ltd.) as a main polymer which is 500,000 parts by weight was dissolved by 500 parts by weight of a plasticizer (isoparaffinic oil IP solvent 2835; manufactured by Idemitsu Petrochemicals Co., Ltd.) And stirred. Then, at an atmosphere temperature of 150 ° C., an alkoxysilane group-containing compound (vinyltriethoxysilane K
After mixing 10 parts by weight of BE1003 (Shin-Etsu Chemical Co., Ltd.) and stirring the mixture uniformly, 1,1-{-t-butylperoxy-3,3,3-5- as an organic peroxide was used.
2. Trimethylcyclohexane (manufactured by NOF Corporation)
08 parts by weight were added, and the mixture was stirred uniformly to perform a functional group reaction (grafting). Then, after removing the low molecular weight under reduced pressure, 2 parts by weight of dibutyltin dilaurate (DBTDL) as a silanol condensation catalyst was added. Then, after performing an appropriate decompression treatment, the mixture was poured into a mold at a low pressure and solidified by cooling to obtain an intermediate molded product. The intermediate molded product was immersed in water at room temperature for 48 hours to conduct condensation by alcoholic dealation using water and three-dimensional crosslinking to obtain a soft elastomer composition of Example 1.

Example 2 100 parts by weight of SEPS (Septon 4055; manufactured by Kuraray Co., Ltd.) which is a high-molecular-weight styrene-based thermoplastic elastomer (molecular weight: about 200,000)
11. 1200 parts by weight of the same plasticizer as in Example 1, 20 parts by weight of the alkoxysilane group-containing compound, and 12 parts by weight of the organic peroxide.
A composition was obtained in the same manner as in Example 1, except that 08 parts by weight and 4 parts by weight of a silanol condensation catalyst were used.

Example 3 SEPS (Septon 200
2; 90 parts by weight of Kuraray Co., Ltd.) and 100 parts by weight of a main polymer obtained by mixing 10 parts by weight of a SIS styrene-based superplastic elastomer (JSRTR2004; manufactured by Japan Synthetic Rubber Co., Ltd.), and a plasticizer 100 Parts by weight, 10 parts by weight of an alkoxysilane group-containing compound, 8.5 parts of an organic peroxide
A composition was obtained in the same manner as in Example 1, except that 4 parts by weight of the silanol condensation catalyst was used.

[Embodiment 4] The same SEPS90 as in Embodiment 1
11. Organic peroxide 12 per 100 parts by weight of main polymer obtained by mixing 10 parts by weight of SIS of Example 3 with 10 parts by weight of SIS of Example 3.
A composition was obtained in the same manner as in Example 1, except that 08 parts by weight and 4 parts by weight of a silanol condensation catalyst were used.

Example 5 A composition was obtained in the same manner as in Example 4, except that the compounding amount of the alkoxysilane group-containing compound was 20 parts by weight.

Example 6 90 parts by weight of SEBS and SIS
A composition was obtained in the same manner as in Example 2 except that a main polymer mixed with 10 parts by weight was used.

Example 7 Example 6 was repeated except that 2000 parts by weight of a plasticizer, 30 parts by weight of an alkoxysilane group-containing compound, 24.16 parts by weight of an organic peroxide and 8 parts by weight of a silanol condensation catalyst were used. A composition was obtained in the same manner.

Comparative Example 1 Same SEBS10 as in Example 1.
500 parts by weight of a plasticizer was mixed and stirred at 180 ° C. with respect to 0 parts by weight to obtain a composition. The solubility was good.

Comparative Example 2 Same SEPS10 as in Example 2
1200 parts by weight of a plasticizer was mixed and stirred at 180 ° C. with respect to 0 parts by weight to obtain a composition.

Appropriate test pieces were prepared from the compositions of the above Examples and Comparative Examples, and were subjected to the following characteristic tests.

[100% M] Tensile test (JIS K63)
01 based) and a 100% elongation, the lower the value (modulus), the softer it is.

[Compression load] Sample size φ1.24mm ×
A value obtained by compressing a 12 mm test piece by 25% (JIS
K6301), and the lower this value is, the softer it is.

[Compression permanent set] φ29.0 mm × 12.7
After compressing a 25 mm test piece by 25%, the residual strain rate (according to JIS K6301) after keeping the temperature at 70 ° C. × 22 hr was measured.

[Gel Fraction] A test piece was put in toluene at a rate of 1 g per 100 g of toluene at 37 ° C. for 4 days, and then dried in a dryer at an ambient temperature of 60 ° C. for 2 days. Was measured, and the difference from the original weight was defined as the gel fraction. This gel fraction indicates the proportion of the polymer insoluble in toluene and is expressed by the following formula. Since the styrene-based elastomer is a good solution in toluene, the gel fraction increases if crosslinking is performed.

[0036]

(Equation 1)

[Thermal expansion change point] Thermal analyzer (TMA40)
10; manufactured by Mac Science Co., Ltd.)
mm test piece was placed in a tank, and a load of 3 g was applied to the upper part of the test piece, and the temperature was increased at a rate of 10 ° C./min. The temperature was measured.

[Shape Retention Test] The sample was placed in a constant temperature bath at an ambient temperature of 70 ° C. for 20 days, and the difference from the original height was shown in percentage.

As is clear from the test results shown in Table 1,
Examples 1 to 7 and Comparative Examples 1 and 2 were all [100%
M] and [compression load] are 7 kg / cm or less, which indicates that the soft elastomer has a sufficiently low altitude and flexibility.

The [gel fraction] is 0% in the comparative example, but is 90% or more in all of Examples 1 to 7. In Examples 1 to 7, the crosslinking was sufficiently performed. I understand. As a result, [shape retention] was 60 in Comparative Examples 1 and 2.
% Or less, whereas Examples 1 to 7 all have 90% or more, and it can be seen that the example has significantly improved heat resistance as compared with the comparative example.

Claims (6)

[Claims] An excess of a plasticizer and / or a main polymer containing hydrogenated styrene-isoprene-styrene copolymer (SEPS) or hydrogenated styrene-butadiene-styrene copolymer (SEBS) as a main component. After blending the softener, the alkoxysilane group-containing compound is subjected to a graft reaction using an organic peroxide, and then molded by injection molding at a low pressure, then solidified by cooling, and then condensation by dealcoholization using water. And a method for producing a soft elastomer composition, wherein three-dimensional crosslinking is performed. 2. 100 parts by weight of the main polymer, 300 to 2500 parts by weight of a plasticizer, 0.5 to 50 parts by weight of an alkoxysilane group-containing compound, 0.1 to 30 parts by weight of an organic peroxide, 0.1 to 2 silanol condensation catalyst
The method for producing a flexible elastomer composition according to claim 1, wherein 0 part by weight is blended. 3. The soft elastomer according to claim 1, wherein the condensation and three-dimensional cross-linking steps are performed by exposing to warm water of 50 ° C. or lower or exposing to atmospheric moisture. A method for producing the composition. 4. A soft elastomer composition produced by the production method according to claim 1, wherein a plasticizer is used in an amount of 300 to 2500 based on 100 parts by weight of the main polymer.
Parts by weight, 0.5 to 50 parts by weight of an alkoxysilane group-containing compound.
A soft elastomer composition comprising 0.1 to 30 parts by weight of an organic peroxide and 0.1 to 20 parts by weight of a silanol condensation catalyst. 5. The method according to claim 1, wherein 100 parts by weight of the main polymer is
Styrene-isoprene-styrene copolymer (SIS),
Or a styrene-butadiene-styrene copolymer (SB
5. The soft elastomer composition according to claim 4, which contains 0.5 to 20 parts by weight of S). 6. The flexible elastomer composition according to claim 4, wherein the gel fraction after crosslinking is 90% or more.