JPH05310869A - New ester compound, production thereof, and use thereof as cocross-linker of acrylic rubber - Google Patents

Abstract

PURPOSE:To prevent light scattering due to microphase separation or clouding and thus improve clarity and mechanical strengths by using a specific diester compd. as a cocross-linker of an alkyl (meth)acrylate-dicyclopentenylated (meth) acrylate copolymer rubber. CONSTITUTION:An alkyl (meth)acrylate-dicyclopentenylated (meth) acrylate copolymer rubber is obtd. by copolymerizing 60-94mol% alkyl (meth)acrylate with 1-30wt.% dicyclopentenylated (meth)acrylate in soln. in the presence of up to 0.2mol% chain transfer agent and purifying the copolymn. product by reprecipitation. 100 pts.wt. the rubber is compounded with 1-20 pts.wt. diester compd. of the general formula (wherein R is 1-8C alkyl; and n is 10-30) as a cocross-linker and 2 pts.wt. or lower cross-linking initiator (e.g. org. peroxide) and cross-linked by heating or irradiation with active energy rays, etc.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a novel ester compound,
The manufacturing method and the co-crosslinking agent for acrylic rubber using the same. More specifically, it relates to a novel ester compound effectively used as a co-crosslinking agent for a transparent acrylic rubber composition, a method for producing the same, and a co-crosslinking agent for an acrylic rubber using the same.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication (Kokai) No. 63-256902 discloses a (meth) acrylic acid ester whose ester group is an alkyl group, a dicyclopentenyl group or the like and a general formula CH ₂ = CRCO (OCH ₂ CH ₂ ) nOC.
A synthetic resin optical transmission medium comprising a copolymer with di (meth) acrylate in which OCR = CH ₂ [R: H, CH ₃ ] is described.

However, in this synthetic resin optical transmission body molded as a core material or the like, the above-mentioned (meth) acrylic acid ester and di (meth) acrylate are injected as a monomer mixture into a tube serving as a clad material. Since heat polymerization is performed in the tube, volume shrinkage occurs due to the progress of polymerization, "sink marks" occur in the tube, the surface of the polymer that becomes the core material loses smoothness, and the roundness collapses. When the monomer mixture is injected, the pump must be injected at an extremely low speed, or the pump must be kept running for the purpose of pressurizing, the publication describes.

Such a polymerization operation is not only complicated, but it cannot avoid the inhomogeneity associated with gelation.
In addition, unreacted monomers obviously remain, and scattering caused by nonuniformity of the refractive index caused by such a phenomenon causes a problem that the transparency of the optical transmission medium is low.

In addition, the applicant previously found that ethyl acrylate
-Dicyclopentenyl acrylate (molar ratio 90:10) 100 parts by weight of tetraethylene glycol diacrylate 10 parts by weight and 0.5 parts of organic peroxide (Nippon Oil & Fats Products Perhexa 3M) were cross-linked and molded. Obtained as a Fresnel lens (Japanese Patent Laid-Open No. 3-6501).

When this compound is cross-linked, the double bond of tetraethylene glycol diacrylate is higher in reactivity than the double bond derived from the dicyclopentenyl group in the copolymer, so that the latter also co-crosslinks. However, homopolymerization also progresses considerably, and the compatibility with the above copolymer is reduced.

Such a decrease in compatibility is apt to cause microphase separation, and this phenomenon is more likely to occur as the blending ratio of tetraethylene glycol diacrylate increases. As a result, the crosslinked product causes uneven refractive index and white turbidity and scatters light to reduce transparency, and also becomes unsatisfactory in terms of mechanical strength such as tensile strength.

[0008]

DISCLOSURE OF THE INVENTION The object of the present invention is that it does not cause uneven refractive index or white turbidity due to the presence of unreacted monomers and gels or microphase separation, and is also excellent in mechanical strength. (EN) It is intended to provide a novel ester compound effectively used as a co-crosslinking agent for a transparent acrylic rubber composition giving a crosslinked product, and a method for producing the same.

Another object of the present invention is to provide a co-crosslinking agent for acrylic rubber, which comprises the novel ester compound, and a transparent acrylic rubber composition using the same.

[0010]

According to the present invention, the general formula (Where R is an alkyl group having 1 to 8 carbon atoms, and n is 10 to 3
A novel ester compound represented by the formula (I is an integer of 0) is provided.

The novel ester compound is produced by reacting an alkyl acrylate oligomer having hydroxyl groups at both ends with 2-dicyclopenten-1-ylacetic acid.

Alkyl acrylate oligomers having a hydroxyl group (esterified with an excess amount of acetic acid and 95% or more of the remaining acetic acid are hydroxyl groups) at both ends are alkyl acrylate oligomers having an alkyl group having 1 to 8 carbon atoms. A polymerization initiator or chain transfer agent having a hydroxyl group, preferably the former, is used to obtain a polymerization reaction at about 40 to 100 ° C. for about 5 to 10 hours. As the polymerization initiator having a hydroxyl group,
For example, hydrogen peroxide, 2,2'-azobis (2-cyanopropanol), etc. is about 0.1 per 100 parts by weight of alkyl acrylate.
~ 5 parts by weight, preferably about 1 to 2 parts by weight is used, and as the chain transfer agent having a hydroxyl group, for example, 2-mercaptoethanol is about 0.1 to 5 parts by weight, preferably about 100 parts by weight per 100 parts by weight of alkyl acrylate. It is used in an amount of 0.5 to 2 parts by weight.

The degree of polymerization of the resulting oligomer is about 10-30.
The polymerization conditions are adjusted to be within the range. When an oligomer having a degree of polymerization smaller than this is used, the reaction between the oligomers easily occurs, the crosslinking reaction with the core copolymer rubber hardly occurs, and as a result, the rubber containing the cured product of only the oligomer becomes hard, The growth will stop. On the other hand, when an oligomer having a degree of polymerization higher than this is used, the crosslinking reaction with the copolymer rubber becomes difficult to occur, cross-linking at high temperature or for a long time is required, and the cross-linking density becomes small. Will be reduced.

The thus obtained alkyl acrylate oligomer having 95% or more hydroxyl groups at both ends is
It is diesterified by reaction with 2-cyclopenten-1-yl acetic acid in the presence of sodium alkoxide in a lower alcohol at about 60-100 ° C. During this reaction, a polymerization inhibitor such as p-methoxyphenol or phenothiazine is added to the reaction system in order to prevent further polymerization of the oligomer.

The diester compound obtained is an alkyl
(Meth) acrylate-dicyclopentenyl group-containing (meth)
It is effectively used as a co-crosslinking agent for acrylate copolymer rubber.

The alkyl (meth) acrylate-dicyclopentenyl group-containing (meth) acrylate copolymer is
Alkyl (meth) acrylate and the general formula CH ₂ ═CR ₁ COOR ₂ or CH ₂ ═CR ₁ COO (CH ₂ ) nOR ₂ (wherein R ₁ is a hydrogen atom or a methyl group, and R ₂ is a dicyclopentenyl group. And
n is 1 or 2) dicyclopentenyl
A copolymer with (meth) acrylate or dicyclopentenyloxyalkyl (meth) acrylate is used.

Main component of such copolymer (about 60-94 mol%)
Examples of the alkyl (meth) acrylate that forms an alkyl acrylate having an alkyl group having 1 to 12 carbon atoms such as methyl, ethyl, n-butyl, isobutyl, 2-ethylhexyl, octyl and dodecyl, or hexyl, octyl, decyl and dodecyl. Alkyl methacrylate having an alkyl group having 6 to 12 carbon atoms is used. The number of carbon atoms of the methacrylate is limited to 6 or more, because of the relationship with the glass transition point, within the range of obtaining a copolymer showing rubber-like elasticity at room temperature, alkyl methacrylate having 5 or less carbon atoms 3 There is no problem even if it is copolymerized with the original or more.

The (meth) acrylate represented by the above-mentioned two general formulas, which is copolymerized with these alkyl (meth) acrylates, is used as a crosslinking point forming monomer in the copolymer.
1 to 30% by weight, preferably about 5 to 20% by weight, are copolymerized.
Further, in such a copolymer, vinyl monomers having copolymerizability with these comonomers, preferably about 40 mol% or less of alkyl methacrylate, etc., preferably about 4 to 20 mol.
It is also possible to copolymerize at a ratio of%.

The copolymerization reaction is carried out by a solution polymerization method, an emulsion polymerization method or the like, but the solution polymerization method is most suitable because it is an essential condition that gelation does not occur. that time,
It is preferable to add a chain transfer agent represented by an organic mercapto compound at a ratio of about 0.2 mol% or less with respect to the monomer mixture, which effectively prevents gelation of the copolymer. After the completion of the polymerization reaction, the copolymer is purified by a method such as reprecipitation to remove unreacted monomers, oligomers and other impurities.

The diester compound represented by the above general formula is added to the copolymer as a co-crosslinking agent.
Such a co-crosslinking agent has almost the same reactivity as the crosslinkable group in the copolymer derived from the dicyclopentenyl group,
This prevents microphase separation due to homopolymerization of the co-crosslinking agent, that is, deterioration of transparency due to light scattering. The co-crosslinking agent is used in a proportion of about 1 to 20 parts by weight, preferably about 10 to 15 parts by weight, based on 100 parts by weight of the copolymer.

The composition comprising the copolymer and the diester compound co-crosslinking agent is crosslinked by heating or irradiation with active energy rays. At that time, a crosslinking initiator generally used with an organic peroxide is used for crosslinking. The crosslinking initiator is used in a proportion of about 2 parts by weight or less per 100 parts by weight of the copolymer, but even if the crosslinking initiator is not used, a radical is generated, and if a crosslinking reaction occurs, the crosslinking initiator may be used without using it. Good.

[0022]

The copolymer of alkyl (meth) acrylate and dicyclopentenyl (meth) acrylate or dicyclopentenyloxyalkyl (meth) acrylate is co-crosslinked with a polyfunctional unsaturated compound, in which case a co-crosslinking agent is used. By selecting the reactivity of, that is, by selecting a new diester compound having the same reactivity as the crosslinkable group in the copolymer, light scattering due to microphase separation and white turbidity is prevented, and the transparency is excellent. In addition to obtaining an acrylic rubber crosslinked product, it is possible to improve the mechanical strength (tensile strength etc.) of the crosslinked product.

[0023]

EXAMPLES The present invention will now be described with reference to examples.

Reference Example 1 100 parts (weight, hereinafter the same) of a monomer consisting of 90 mol% of ethyl acrylate and 10 mol% of dicyclopentenyl acrylate, 1.64 parts of azobisisobutyronitrile, 0.9 part of mercaptoethanol and 721 parts of methyl ethyl ketone was added, and a polymerization reaction was carried out at 54 ° C. for 3 hours while bubbling nitrogen gas in a separable flask. Then 5 ℃
After cooling to below and stopping the polymerization reaction, reprecipitation with a 30 wt% methanol aqueous solution (poor solvent) and methyl ethyl ketone (good solvent) was repeated 5 times to remove unreacted monomers, etc. Polymer A was obtained.

Reference Example 2 Using 100 parts of a monomer consisting of 90 mol% n-butyl acrylate and 10 mol% dicyclopentenyl acrylate, a polymerization reaction was carried out in the same manner as in Reference Example 1 to obtain a copolymer B. It was

Example 1 900 g of ethyl acrylate, 20 g of 30% hydrogen peroxide and 1000 g of dimethylformamide were placed in a separable flask having a volume of 2 L, and the mixture was kept at 80 ° C. while bubbling nitrogen gas.
The polymerization reaction was carried out for 6 hours. The reaction mixture was cooled to 5 ° C. or lower and then concentrated with a vacuum dryer (1 Torr, 80 ° C.) to obtain an acrylic oligomer having a hydroxyl group at both ends (degree of polymerization: about 20).

100 g of the obtained acrylic oligomer containing hydroxyl groups at both ends was dissolved in 150 g of methanol, 50 g of sodium methoxide was added, and the mixture was stirred at room temperature for 2 hours. Then p-
Methoxyphenol (1 g) and 2-cyclopenten-1-ylacetic acid (100 g) were added, and the mixture was stirred at 60 ° C for 6 hours. The reaction mixture was concentrated at room temperature under reduced pressure (1 Torr), the residue was washed with 5% sodium hydroxide in ethyl acetate solution to remove sodium methoxide and p-methoxyphenol, and the mixture was left at room temperature under reduced pressure.
Concentration at (1 Torr) gave the desired diester compound.

An acrylic rubber composition was prepared by adding 10 parts of this diester compound and 1 part of an organic peroxide (Nippon Oil and Fats Product Perhexa 3M) to 100 parts of the copolymer A obtained in Reference Example 1 above. The composition was compression molded at 120 ° C. for 20 minutes to obtain a 100 × 100 × 2 mm transparent acrylic rubber sheet.

Example 2 In Example 1, instead of the copolymer A, the same amount of the copolymer B obtained in Reference Example 2 was used.

Comparative Example 1 In Example 1, the same amount of tetraethylene glycol diacrylate was used instead of the diester compound.
A transparent acrylic rubber sheet was obtained by compression molding at 8 ° C. for 8 minutes.

Comparative Example 2 In Example 2, the same amount of tetraethylene glycol diacrylate was used instead of the diester compound.
A transparent acrylic rubber sheet was obtained by compression molding at 8 ° C. for 8 minutes.

The following items were measured for the transparent acrylic rubber sheets obtained in each of the above Examples and Comparative Examples. Light transmittance: UV-VIS spectrophotometer (Hitachi spectrophotometer U-400
Measured with 0) Tensile strength: Measured with an autograph (DSS-5000 manufactured by Shimadzu Corporation) according to JIS K-6301 Measurement item Real-1 Real-2 Ratio-1 Ratio-2 Light transmittance (%) 99 99 97 97 Tensile strength Strength (kgf / cm ² ) 61 53 53 48

[Brief description of drawings]

FIG. 1 is the absorbance of the diester compound obtained in Example 1.
It is an infrared absorption spectrum showing (ABS).

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI Technical display location C08K 5/10 7242-4J C08L 33/08 LHW 7921-4J

Claims (4)

[Claims] 1. A general formula (Where R is an alkyl group having 1 to 8 carbon atoms, and n is 10 to 3
Which is an integer of 0). 2. A process for producing a novel ester compound according to claim 1, wherein an alkyl acrylate oligomer having hydroxyl groups at both ends is reacted with 2-dicyclopenten-1-ylacetic acid. 3. A co-crosslinking agent for an alkyl (meth) acrylate-dicyclopentenyl group-containing (meth) acrylate copolymer rubber, which comprises the novel ester compound according to claim 1. 4. A transparent acrylic rubber composition comprising an alkyl (meth) acrylate-dicyclopentenyl group-containing (meth) acrylate copolymer and the novel ester compound according to claim 1.