JPH11209443A - Curable resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a curable resin composition which can give a molding having excellent transparency and impact resistance and high modulus and can be desirably used for castings such as artificial marble. SOLUTION: There is provided a curable resin composition comprising (A) a polymer comprising units of an alkyl (meth)acrylate monomer with a 12C or higher alkyl and units of other monomers and having at least two methacryloyl groups on the average per molecule; (B) a methacrylic ester monomer; and (C) radical-generating polymerization initiator. It is desirable that the amount of polymer A used is 0.5-30 wt.% based on the total weight of polymer A and monomer B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a curable resin composition used for casting polymers such as a transparent acrylic plate or an artificial marble, which is required to have high transparency and impact resistance and high elastic modulus. It is about.

[0002]

2. Description of the Related Art A drawback of an acrylic resin molded article produced by casting polymerization, such as a transparent acrylic plate or an acrylic artificial marble, is a lack of impact resistance. It is said that the cause is internal stress at the time of curing, poor curing of the resin itself, and the like. As a means for improving the stress, a method of adding a high molecular weight anti-shrinkage agent (JP-A-5-124844, JP-A-185021), a method of adding a macromonomer (JP-A-8-135802), and a method of adding a polyfunctional low-molecular-weight monomer (JP-A-8-135802).
No. 231610) has been proposed. However, since the anti-shrinkage agent is not copolymerized with the alkyl methacrylate monomer, and since the macromonomer has a high molecular weight and is monofunctional although it is copolymerized with the alkyl methacrylate monomer, depending on the curable composition containing them, The impact resistance of the resulting molded article was still insufficient.
Furthermore, the addition of the polyfunctional low molecular weight monomer has a problem that the internal stress is generated and the elastic modulus is lowered. On the other hand, in the field of optical materials, an invention utilizing a derivative derived from dimer diol having a large molecular weight, that is, dimer diol dimethacrylate has been proposed (JP-A-9-13).
No. 6861). However, the molded article obtained by the present invention also has a problem that the elastic modulus is low.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a curable resin composition which gives a methacrylic resin molded article having excellent impact resistance and a high elastic modulus.

[0004]

Means for Solving the Problems The present inventors have made intensive studies to solve the above problems, and as a result, have completed the present invention. That is, the present invention comprises (A) an alkyl (meth) acrylate monomer unit having an alkyl group having 12 or more carbon atoms and other monomer units, and has an average of two or more methacryloyl groups per molecule. Polymer,
It is a curable resin composition comprising (B) a methacrylate monomer and (C) a radical-generating polymerization initiator.
Hereinafter, the present invention will be described in more detail.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The polymer of the above component (A) is synthesized as follows. That is, first, an alkyl (meth) acrylate having an alkyl group having 12 or more carbon atoms,
Thereafter, a precursor compound is obtained by polymerizing a vinyl compound having a functional group necessary for introducing a methacryloyl group into the polymer (referred to as a methacryloyl group-introducing vinyl compound) and, if necessary, a monomer copolymerizable therewith. Examples of the alkyl (meth) acrylate having an alkyl group having 12 or more carbon atoms [hereinafter referred to as long-chain alkyl (meth) acrylate] include lauryl (meth) acrylate and stearyl (meth) acrylate.

The vinyl compound for introducing a methacryloyl group has a hydroxyl group such as 2-hydroxyethyl (meth) acrylate, one terminal (meth) acrylate of polyethylene glycol, and one terminal (meth) acrylate of polycaprolactone. (Meth) acrylates having epoxy groups such as (meth) acrylates and glycidyl (meth) acrylates, isocyanates such as isocyanate methacrylate, isocyanate ethyl methacrylate or 1- (isopropenylphenyl-1,1-dimethylmethyl isocyanate) Vinyl compounds having a group are preferred, and further, (meth) acrylic acid,
Monomers that relatively easily perform esterification or transesterification, such as methyl (meth) acrylate or ethyl (meth) acrylate, can also be used. Further, as a monomer copolymerizable with the above-mentioned monomer, (meth) acrylic acid ester, styrene, (meth) acrylic acid and the like are preferable.

These precursors are heated and polymerized in a solvent such as toluene, ethyl acetate or methyl ethyl ketone at 80 to 120 ° C. in the presence of an initiator such as azobisisobutyronitrile to obtain a precursor polymer. Can be If necessary, a chain transfer agent such as ethyl mercaptan or dodecyl mercaptan may be added during polymerization.

Next, the precursor polymer thus obtained is reacted with a reactive compound having a methacryloyl group (hereinafter referred to as a methacryloyl compound) to obtain a desired polymer. The methacryloyl compound used varies depending on the functional group in the precursor polymer. For example, when the functional group in the precursor polymer is a hydroxyl group, a lower methacrylate such as methacrylic acid or methyl methacrylate is introduced by an esterification reaction or transesterification, or a methacrylate compound having an isocyanate group is reacted. Let me introduce.

When the functional group is a carboxylic acid, a methacrylate having a hydroxyl group such as 2-hydroxyethyl methacrylate, methacrylate at one end of polyethylene glycol, methacrylate at one end of polycaprolactone, and glycidyl methacrylate. And methacrylic esters having an epoxy group. When the functional group is an epoxy group, a methacryloyl compound having a carboxyl group such as methacrylic acid is used. When the functional group is an isocyanate group, methacrylic acid 2-
A methacrylic acid ester having a hydroxyl group such as hydroxyethyl, polyethylene glycol one-terminal methacrylate, polycaprolactone one-terminal methacrylate, etc. is reacted. When the functional group is an ester having a lower alkyl group such as a methoxycarbonyl group or an ethoxycarbonyl group, transesterification such as titanium tetraisopropoxide with a methacrylic acid ester having a hydroxyl group such as 2-hydroxyethyl methacrylate. By reacting using a catalyst, a methacryloyl group is introduced.

The polymer (A) can be produced by the above method. (A) In the polymer, the ratio of the long-chain alkyl (meth) acrylate monomer unit is 10% by weight.
It is preferably at least the above, and a preferable upper limit is 80% by weight. Furthermore, the content of the methacryloyl group in the polymer (A) needs to be 2 or more on average per molecule, and preferably 3 or more on average per molecule of polymer. If the number of methacryloyl groups per polymer is less than 3 on average, it is difficult to improve the elastic modulus of the obtained cured molded article. (A) The preferred molecular weight of the polymer is a number average molecular weight determined by GPC measurement of 2000 to 3
0000. When the molecular weight is less than 2,000, a polymer partially containing no functional group is easily generated, and the mechanical strength of the cured molded article is reduced. On the other hand, if the molecular weight is larger than 30,000, the compatibility with other monomers deteriorates, and the viscosity of the curable composition becomes too high. More preferably,
3000 to 20,000.

In the present invention, the (B) methacrylate monomer dissolves (A) the polymer and (C) a radical-generating polymerization initiator described in detail below, and has a fluidity suitable for casting. It is a reactive diluent for obtaining a liquid resin composition having the same. Specific examples of the (B) methacrylate monomer include methyl methacrylate, ethyl methacrylate, butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, and methacryl. Monofunctional alkyl methacrylates such as lauryl acrylate, stearyl methacrylate, isostearyl methacrylate and isobornyl methacrylate; polyethylene glycol polymethacrylate, polypropylene glycol polymethacrylate, polytetramethylene glycol polymethacrylate, polycaprolactone polymethacrylate, polyester polyol polymethacrylate , Polyurethane polymethacrylate, trimethylolpropane trimethacrylate, pentaerythritol poly Methacrylate and polyfunctional methacrylic acid esters, such as dimer diol dimethacrylate, etc. These may be used singly or in combination. The preferred (B) methacrylate monomer is dimer diol dimethacrylate in that a molded article having an excellent elastic modulus is obtained.

The preferable ratio of the component (A) is 0.5 to 3 based on the total amount of the components (A) and (B).
0% by weight. When the proportion of the component (A) is less than 0.5% by weight, the obtained molded article has poor impact resistance.
If it is more than 10% by weight, the viscosity of the resin composition is too high and casting becomes difficult.

Specific examples of the radical-generating polymerization initiator (C) in the present invention include peroxides such as benzoyl peroxide, octanoyl peroxide, lauroyl peroxide and di-t-butyl peroxide; And nitrogen compounds such as butyronitrile. The preferred use amount of the component (C) is 0.5 to 3% by weight based on the total amount of the components (A) and (B). The curable resin composition of the present invention essentially contains the components (A), (B) and (C), but may further contain a chain transfer agent, a pigment or the like. Further, the curing reaction, that is, the polymerization of the curable resin composition is usually performed at a temperature of 5 ° C.
It is preferably performed at 0 to 150 ° C. for 2 to 20 hours.
Hereinafter, the present invention will be described more specifically with reference to Reference Examples, Examples, and Comparative Examples. In addition, the dimer diol dimethacrylate used in the examples is described in JP-A-9-136861.
The synthesis was carried out according to the method described in JP-A No.

[0013]

Reference Example 1 (Synthesis of polymer A1) Dimroth condenser,
In a flask equipped with two dropping funnels, as initial charge, stearyl methacrylate (36.5 parts), glycidyl methacrylate (9.1 parts), dodecyl mercaptan (3.4 parts), toluene (63.1 parts) Was put. After raising the temperature of the reaction solution to 92 ° C., from one dropping funnel,
Stearyl methacrylate (36.5 parts), glycidyl methacrylate (9.1 parts) and dodecyl mercaptan (3.4 parts) were added dropwise over 2 hours, and azobisisobutyronitrile ( 1 part) and toluene (26.3 parts) were added dropwise over 3 hours. After heating for an additional hour, azobisisobutyronitrile (1
Parts) and toluene (10.5 parts) were added dropwise over 1 hour. After the completion of the dropwise addition, the mixture was heated for 3 hours to obtain a polymer having an epoxy group. To this reaction liquid (200 parts), tetrabutylammonium bromide (1 part), methacrylic acid (5 parts) and 6-t-butyl-
2,4-Xylenol (0.05 part) was added and reacted for 9 hours. The polymer A1 thus obtained has a number-average molecular weight of 3200 from the result of measurement of the molecular weight by GPC, and has about 4 methacryloyl groups in one molecule based on the concentration of the methacryloyl group obtained by NMR measurement. I knew it was.

[0014]

Reference Example 2 (Synthesis of Polymer A2)
Stearyl methacrylate (27.4 parts), glycidyl methacrylate (18.6 parts), dodecyl mercaptan (3.4 parts), and toluene (63.1 parts) were added, and stearyl methacrylate (27) was added from one dropping funnel. .4
Parts), glycidyl methacrylate (18.6 parts), and dodecyl mercaptan (3.4 parts) were added dropwise over 2 hours to obtain polymer A2 in the same manner as in Reference Example 1. The polymer A1 thus obtained has a number average molecular weight of 3300 from the measurement result of the molecular weight by GPC, and has about 8 methacryloyl groups in one molecule based on the concentration of the methacryloyl group obtained by NMR measurement. I knew it was.

[0015]

Examples 1 and 2 Benzoyl peroxide (1 part) was added to a mixture of polymer A1 (10 parts) and dimer diol dimethacrylate (95 parts) to obtain a curable resin composition (Example 1). ). The composition is poured into a box made of release paper, 55 ° C, 10 hours, 70 ° C, 5 hours, 100 ° C,
A test plate was obtained by heating for hours. The following physical properties were measured using the obtained test plates, and the results are shown in Table 1. -Evaluation of elastic modulus: The flexural modulus was evaluated according to the method of JIS K-7203. The sample used for evaluation was 8 cm in length, 1 cm in width, and 0.4 cm in thickness. -Evaluation of impact strength: Impact strength was evaluated according to the method of JIS K-7110. The same operation as in Example 1 was performed for the polymer A2, and the physical properties of the prepared test plate were measured (Example 2).

[0016]

Comparative Example 1 A test plate was prepared from dimer diol dimethacrylate alone, and the same measurement as in Example 1 was performed.

[0017]

[Table 1]

[0018]

The cured product obtained from the curable resin composition of the present invention has a high elastic modulus and an excellent impact strength. Having such characteristics, the resin composition is particularly suitable for molding a transparent acrylic plate or artificial marble.

Claims (4)

[Claims] 1. A polymer comprising (A) an alkyl (meth) acrylate monomer unit having an alkyl group having 12 or more carbon atoms and another monomer unit and having an average of two or more methacryloyl groups per molecule. A curable resin composition comprising the unified polymer, (B) a methacrylic acid ester monomer, and (C) a radical-generating polymerization initiator. 2. The ratio of the polymer (A) based on the total amount of the polymer (A) and the monomer (B) methacrylate monomer is 0.5 to 30% by weight. Curable resin composition. 3. The curable resin composition according to claim 1, wherein the polymer (A) has an average of three or more methacryloyl groups per molecule. 4. The curable resin composition according to claim 1, wherein part or all of the (B) methacrylate monomer is dimer diol dimethacrylate.