JPH07173224A - Cocross-linker for transparent acrylic rubber - Google Patents

Abstract

PURPOSE:To provide cocross-lnker which is used for cross-linking an alkyl (meth)acrylate/dicyclopentenyl-contg. (meth)acrylate copolymer rubber, prevents microphase separation or light scattering due to clouding, and gives a cured item excellent in transparency by selecting a specific diester compd. CONSTITUTION:This cocross-linker is a diester compd. of the formula: ROCO (CH2)nC00R (wherein R is dicyclopentenyl; and n is 5-12)(e.g. one obtd. by reacting suberoyl or undecanoyl dichloride with hydroxydicyclopentadiene).

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a co-crosslinking agent for transparent acrylic rubber. More specifically, it relates to a co-crosslinking agent for an alkyl (meth) acrylate-dicyclopentenyl group-containing (meth) acrylate copolymer rubber.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication (Kokai) No. 63-256902 discloses a (meth) acrylic acid ester having an ester group such as an alkyl group or a dicyclopentenyl group 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 carried out in the tube, volume shrinkage occurs due to the progress of polymerization, "sinking" occurs in the tube, the surface of the polymer as 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 inhomogeneity associated with gelation.
In addition, unreacted monomer is apparently left, and scattering caused by nonuniformity of the refractive index caused by such a problem causes a problem that the transparency of the optical transmission body is low.

In addition, the applicant has previously reported that ethyl acrylate
-Crosslinked molding of 100 parts by weight of dicyclopentenyl acrylate (molar ratio 90:10) copolymer with 10 parts by weight of tetraethylene glycol diacrylate and 0.5 parts of organic peroxide (Nippon Oil & Fat Products Perhexa 3M). Obtained as a Fresnel lens (Japanese Patent Laid-Open No. 3-6501).

When this compound is crosslinked, the double bond of tetraethylene glycol diacrylate has a higher reactivity than the double bond derived from the dicyclopentenyl group in the copolymer, so that the latter also cocrosslinks. Homopolymerization also progresses considerably, and the compatibility with the above copolymer is reduced.

Such a decrease in compatibility tends to cause microphase separation, and this phenomenon tends to occur as the proportion of tetraethylene glycol diacrylate increases. As a result, the crosslinked product causes uneven refractive index and white turbidity, not only scatters light to reduce transparency but 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. It is to provide a co-crosslinking agent for a transparent acrylic rubber which gives a crosslinked product.

[0009]

The object of the present invention is as follows.
Alkyl (meth) acrylate-dicyclopentenyl group-containing (meth) acrylate copolymer as a co-crosslinking agent for rubber, the general formula ROCO (CH ₂ ) nCOOR (wherein R is a dicyclopentenyl group, n is 5 Is an integer of ˜12).

The diester compound represented by the above general formula can be obtained by reacting a dihalide compound represented by the general formula XOC (CH ₂ ) nCOX with hydroxydicyclopentadiene. The reaction between them is carried out at a temperature of room temperature to about 80 ° C. in the presence of a tertiary amine compound catalyst such as pyridine using an amount of a dihalide compound in a molar ratio of about 0.4 to 0.5 with respect to hydroxydicyclopentadiene. It is performed by stirring. After completion of the reaction, the desired diester compound is obtained through steps such as extraction with diethyl ether, washing, drying, and evaporation of the solvent.

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.

As the alkyl (meth) acrylate-dicyclopentenyl group-containing (meth) acrylate copolymer,
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 to form, methyl, ethyl, n-butyl, isobutyl, 2-ethylhexyl, octyl, dodecyl and other alkyl acrylates having an alkyl group having 1 to 12 carbon atoms or hexyl, octyl, decyl, dodecyl. Alkyl methacrylate having an alkyl group having 6 to 12 carbon atoms such as 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 where a copolymer showing rubber-like elasticity at room temperature is obtained, alkyl methacrylate having 5 or less carbon atoms is 3 or less. 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 cross-linking 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 and the like, 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 for use, 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. Co-crosslinking agent, with respect to the crosslinking point in the copolymer, in a molar ratio of about 0.5 to 2.0,
Particularly preferably, it is used in a ratio such that it is about 0.6 to 0.75.

The composition comprising the copolymer and the diester compound co-crosslinking agent is crosslinked by heating, irradiation with active energy rays or the like, and at that time, it is crosslinked by a crosslinking initiator which is generally an organic peroxide. The crosslinking initiator is used in a ratio 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, radicals are generated, and if the crosslinking reaction occurs, the crosslinking initiator may be used without using it. Good.

[0018]

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, i.e., selecting a new diester compound having a lower reactivity than the diacrylate compound, light scattering due to microphase separation and cloudiness is prevented, and an acrylic rubber crosslinked product having excellent transparency is obtained. Not only is it possible to improve the mechanical strength (such as tensile strength) of the crosslinked product.

[0019]

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 94 mol% of ethyl acrylate and 6 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, after 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 and the like, 2 An original copolymer A was obtained.

Reference Example 2 The same polymerization reaction as in Reference Example 1 was carried out using 100 parts of a monomer consisting of 75 mol% n-butyl acrylate, 17 mol% methyl methacrylate and 8 mol% dicyclopentenyl acrylate. (However, the polymerization time was 8 hours), and a ternary copolymer B was obtained.

Example 1 Suberic acid dichloride (4.22 g) and hydroxydicyclopentadiene (6.60 g) obtained by the reaction of HOOC (CH ₂ ) ₆ COOH suberic acid with thionyl chloride were dissolved in 20 ml of dehydrated pyridine and stirred at room temperature. While reacting for 12 hours. After completion of the reaction, the reaction mixture was poured into ice-cooled dilute hydrochloric acid, the oily matter was extracted with diethyl ether, and the extract was washed successively with 2N sulfuric acid, aqueous sodium hydrogen carbonate solution and pure water, and dried over anhydrous sodium sulfate.

The residue obtained by distilling off diethyl ether was recrystallized from isopropanol to give 4.32 g of diester of suberic acid.
(Yield 75%) was obtained. The infrared absorption spectrum of this diester compound is shown in FIG.

Binary copolymer A 10 obtained in Reference Example 1
0 part of this diester compound and 10 parts of organic peroxide
An acrylic rubber composition was prepared by adding 1 part of (Nippon Oil and Fat Products Perhexa 3M), and this composition was compression molded at 130 ° C. for 8 minutes to obtain a 100 × 100 × 2 mm transparent acrylic rubber sheet.

Example 2 In Example 1, instead of the binary copolymer A, the same amount of the ternary 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 on the transparent acrylic rubber sheets obtained in each of the above Examples and Comparative Examples. Transparency: UV-VIS spectrophotometer (MPS-2000 manufactured by Shimadzu Corporation) is used to measure the absorbance at a wavelength of 400 nm. Physical properties: Tensile strength, elongation and 100% modulus values
Autograph according to JIS K-6301 (Shimadzu DSS-5000)
Measured by

Measurement item Actual-1 Actual-2 Ratio-1 Ratio-2 Transparency (ABS) 0.021 0.018 0.035 0.036 Tensile strength (kgf / cm ² ) 76 60 64 47 Elongation (%) 185 170 215 206 100% Modulus (kgf / cm ² ) 8.4 10.0 12.3 9.6

Example 3 In Example 1, 5.06 g of undecanoic acid dichloride was used in place of suberic acid dichloride to obtain 6.54 g of undecanoic acid diester (yield 68%). The infrared absorption spectrum of this diester compound is shown in FIG.

[Brief description of drawings]

FIG. 1 is an infrared absorption spectrum of a diester of suberic acid.

FIG. 2 is an infrared absorption spectrum of a diester of undecanoic acid.

Claims (2)

[Claims] 1. An alkyl (meth) acrylate-comprising a diester compound represented by the general formula ROCO (CH ₂ ) nCOOR (wherein R is a dicyclopentenyl group and n is an integer of 5 to 12). Co-crosslinking agent for (meth) acrylate copolymer rubber containing dicyclopentenyl group. 2. An alkyl (meth) acrylate-dicyclopentenyl group-containing (meth) acrylate copolymer and a general formula ROCO (CH ₂ ) nCOOR (wherein R is a dicyclopentenyl group and n is 5 to 12). A transparent acrylic rubber composition comprising a diester compound represented by