JPS61151212A - Methacrylate copolymer and its production - Google Patents

Abstract

PURPOSE:To obtain the titled copolymer excellent in heat and water resistance, by copolymerizing methyl methacrylate with a methacrylate monomer in the presence of a specified radical polymerization initiator. CONSTITUTION:A methacrylate copolymer of a residual monomer content <=0.2wt% is obtained by mixing 100pts.wt. mixture comprising 10-90wt% methyl methacrylate and 90-10wt% methacrylate monomer having an 8C or higher alicyclic hydrocarbon group in the ester moiety [e.g., (iso)bornyl methacrylate monomer] with, optionally, monomers copolymerizable therewith (e.g., styrene) and copolymerizing the obtained mixture in the presence of a combination of 0.01-0.4pt.wt. radical polymerization initiator of a 10hr selected half-life temperature of 45-80 deg.C (e.g., lauryl peroxide) with 0.05-0.8pt.wt. radical polymerization initiator of a half-life temperature of 90-110 deg.C (e.g., di-t-butyl diperoxyisophthalate).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a methacrylic copolymer having excellent heat resistance and water resistance, and a method for producing the same.

[Conventional technology]

Polymethyl methacrylate resin has excellent transparency in the visible region, mechanical strength, and moldability, so it is used in construction materials, signboards, signs, lighting equipment, furniture, and other products. It is used in a wide range of fields, including industrial parts, arts and crafts, and daily necessities. However, the maximum allowable temperature for use is approximately 100°C.
The resin itself had the disadvantage of being highly water-absorbing, resulting in dimensional changes and warping, and even lowering the allowable temperature limit for use. Many techniques have already been disclosed for this purpose, such as (1) a method of copolymerizing methyl methacrylate with a monofunctional monomer or a polyfunctional monomer (Japanese Unexamined Patent Publication No. 57-153008, 1) A method of carrying out the reaction in two stages during the copolymerization reaction (Japanese Patent Application Laid-Open No. 48-95491)
), ■ Method using specific polymerization initiators, chain transfer agents, and heat stabilizers (JP-A-51-69588, JP-A-5S-
16o1s), ■ A method of mixing other resins with excellent heat resistance during molding (Japanese Patent Laid-Open No. 56-90848), ■ A method of applying post-processing such as surface coating after molding (Japanese Patent Laid-Open No. 55-157107, JP 58-62851),
■A method of copolymerizing with a monomer that has low water absorption and is copolymerizable with methyl methacrylate (Japanese Patent Application Laid-Open No. 58-1547
51, JP-A-58-68251, JP-A-58-136
52, Japanese Unexamined Patent Publication No. 58-162651).

[Problem that the invention seeks to solve]

However, although heat resistance and water resistance can be improved individually according to the disclosed technology, it is not possible to improve heat resistance and water resistance simultaneously, and furthermore, according to methods ① and ③, only copolymerization is required. In this case, not only was it not possible to obtain the expected heat resistance and water resistance, but there was also a problem in that the mechanical strength and weather resistance were reduced, and the characteristics of polymethyl methacrylate resin were impaired.

In view of the above-mentioned current situation, the present inventors conducted intensive studies to improve the heat resistance and water resistance of polymethyl methacrylate resin at the same time. It was discovered that methacrylate esters having a cyclic hydrocarbon group, especially (iso)bornyl methacrylate monomers, are effective, and the amount of residual monomer in the copolymer improves both heat resistance and water resistance. It has been discovered that the performance can be further improved by suppressing this effect within a specific range, leading to the present invention.

That is, the present invention uses a monomer mixture consisting of 1v10 to 90% by weight of methimethacrylate and 90 to 10% by weight of a methacrylic acid ester monomer having an alicyclic hydrocarbon group having 8 or more carbon atoms in the ester moiety. A copolymer obtained by copolymerization, wherein the residual monomer amount contained in the copolymer is 2
A methacrylic copolymer and a method for producing the same, characterized in that the amount is less than 1% by weight, preferably 1% by weight or less, particularly 0.5% by weight or less. The copolymer of the present invention can improve heat resistance and water resistance without impairing the transparency, mechanical strength, and moldability that are characteristics of polymethyl methacrylate resin.

A mixture of methyl methacrylate used in the present invention and a methacrylic ester monomer having an alicyclic hydrocarbon group having 8 or more carbon atoms in the ester moiety (hereinafter sometimes simply referred to as methacrylic ester monomer) The proportion is preferably 90 to 10% by weight of methyl methacrylate monomer.
0 to 20% by weight is used. If the content of methyl methacrylate in the mixed monomer is too high outside this range, the heat resistance and water resistance will clearly improve compared to polymethyl methacrylate resin. On the other hand, if the amount is too low, mechanical strength and moldability will be impaired, and in extreme cases, for example, when removing the cast plate from the glass cell, the surface may be damaged. Cracks occur and brittleness that easily breaks during handling develops. In the present invention, it is possible to add a copolymerizable third monomer to the monomer mixture consisting of methyl methacrylate and the above-mentioned methacrylic acid ester monomer, if necessary. Examples of this include saturated aliphatic or saturated alicyclic (meth) such as ethyl (meth)acrylate, butymu (meth)acrylate, hexyl (meth)acrylate, and cyclohexyl (meth)acrylate. Acrylic esters, styrene, vinyltoluene, chlorostyrene, α
- Vinyl monomers such as methylstyrene, polyethylene glycol dimethacrylates such as (meth)acrylonitrile, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, and triethylene glycol dimethacrylate.

The methacrylic acid ester monomers having an alicyclic hydrocarbon group having 8 or more carbon atoms in the ester moiety used in the present invention include (iso)bornyl methacrylate, fenthyl methacrylate, l-menthyl methacrylate, and adamantyl methacrylate. , dimethyl adamantyl methacrylate, and the like. Among these, the (iso)bornyl methacrylate monomer represented by the following general formula (1) is particularly good.

General formula [1] [In the formula, R+, R2, and R3 each represent a hydrogen atom or a methyl group. ] Next, the amount of residual monomer in the copolymer, which is a main requirement in the present invention, will be explained. It is necessary to suppress the amount of residual monomer in the present invention to 2.0% by weight or less. If this range is exceeded, not only the expected heat resistance and water resistance will not be achieved, but also bubbles will be generated during molding and mechanical strength will be reduced, which is undesirable.

Furthermore, the amount of residual monomer, which is a requirement of the present invention, is reduced to 2.0% by weight.
A method of suppressing this will be explained below. This method includes (
(a) A method in which two radical polymerization initiators having different half-life temperatures selected for 10 hours are used in combination; (b) A method in which the copolymer is subjected to a reprecipitation operation or an extraction operation are effective. Method (a) is more effective in that it is easier to operate, and method (b) is more effective in improving performance. The above two methods will be explained in more detail. First, a method of using a radical polymerization initiator in combination, which is one of the preferred methods for producing the copolymer of the present invention, will be explained.

In the copolymerization reaction between methyl methacrylate and a methacrylic acid ester monomer, it has been difficult to proceed with the polymerization of the remaining monomer using conventional methods. That is, according to the conventional polymerization method of methyl methacrylate, for example, in the cast polymerization method, a radical polymerization initiator such as benzoyl peroxide, azobisisobutyronitrile, lauroyl peroxide, t-butylperoxyisobutyrate, etc. After injecting the methyl methacrylate monomer into two tempered glass cells through a gasket of a predetermined thickness, the mixture was degassed by suction, and then heated at 50 to 90°C for 1 to 10 hours. Polymerization was carried out at 100 to 140°C for 1 to 4 hours to obtain a cast plate with a residual monomer content of 2% by weight or less. When applied to the copolymerization reaction with
In addition, the amount of residual monomer increased as the amount of methacrylic acid ester monomer added increased, and the heat resistance and water resistance did not improve as expected. Therefore, the present inventors conducted various studies on copolymerization conditions, selected a radical polymerization initiator to be used for 10 hours, and conducted a copolymerization reaction using two polymerization initiators with different half-life temperatures. After further detailed study, we found that the selected 10-hour half-life temperature was to use a radical polymerization initiator with a half-life temperature of 45 to 80°C and a radical polymerization initiator with a radical polymerization initiator of 90 to 110°C. We have found that this is effective, leading to the present invention.

Initiators with a selected half-life temperature of 45-80°C for 10 hours used in the present invention include di-n-propyl peroxydicarbonate, di-myristyl peroxydicarbonate, di(2-ethylhexyA/) Baroquine carbonate, octanoyl peroxide, lauroyl peroxide, acetyl peroxide, t-
Examples include butyl peroxy (2-ethylhexanoate), benzoyl peroxide, t-butyl peroxyisobutyrate, and the like.

On the other hand, polymerization initiators having a half-life temperature of 90 to 110°C for 10 hours include 1,1-bis(t-butylperoxy)cyclohexane, t-butylperoxylaurate, cyclohexanone peroxide, t-butylperoxy Ruberoxyisopropyl carbonate, dibutylshibaoxyisophthalate, 2,2-bis(t-butylperoxy)octane, 2,2-bis(t-butylperoxy)butane, di-t-butylshibaoxyisophthalate, etc. can be mentioned.

The amount added is 45 to 80 parts by weight per 100 parts by weight of the mixed monomer.
The half-life temperature of the initiator selected for 10 hours is 0.01~0.
It is used in an amount of 4 parts by weight, preferably in the range of 0.05 to 0.3 parts by weight. Outside this range, if the amount is too low, the initial polymerization rate will actually slow down, and if it is too high, the reaction will proceed rapidly, causing problems such as foaming and bumping, and making it difficult to control the reaction rate. Become. The initiator with a selected 10 hour half-life temperature of 90 DEG to 110 DEG C. is used in the range of 0.05 to 0.8 parts by weight, preferably 0.1 to 0.5 parts by weight.

If it is outside this range and is too small, a sufficient effect to reduce the amount of residual monomer will not be found, and if it is too large, the initiator will remain in the copolymer, causing a decline in physical properties such as weather resistance and coloring. This is undesirable.

Next, another preferred method for producing the copolymer of the present invention, which involves reprecipitation or extraction, will be described. A copolymer of a specific composition obtained by a conventional conventional polymerization method is dissolved and dissolved in a good solvent at room temperature, for example, and then poured into a large amount of a poor solvent to reprecipitate it, and then concentrated.
By repeating the operation of drying the residue multiple times as necessary, residual monomers are removed, and a copolymer with excellent heat resistance and water resistance can be obtained. Good solvents used in this method include acetone, allyl alcohol/l', n-butane chloride, benzene, xylene, toluene, ethyl acetate, methyl acetate, chloroform, carbon tetrachloride, tetrahydrofuran, trichloroethane, ethylene dichloride, Examples include methylene dichloride, and examples of poor solvents used as precipitation media include hexane, petroleum benzene, methyl alcohol (including water-soluble i), water, and the like.

Furthermore, as another preferred method for producing the copolymer of the present invention, a copolymer having a specific composition obtained by a conventional polymerization method is subjected to a predetermined method using a suitable extractor such as a Soxhlet extractor. By performing extraction for a period of time, a copolymer with excellent heat resistance and water resistance from which residual monomers have been removed can be obtained as an extraction residue.

Furthermore, as already known technology, injection molding machines,
It is also effective to suction the remaining monomer from the vent part of an extrusion molding machine or the like in combination with the methods (a) and (b) described above, and it is also possible to use it in the present invention.

Copolymerization methods for producing the copolymer according to the present invention include known polymerization methods that have already been disclosed, such as cast polymerization using a radical polymerization initiator, suspension polymerization, emulsion polymerization, and photopolymerization. It is also possible to use these polymerization methods in combination.

In addition, the methacrylic copolymer based on the present invention may be mixed with other polymers as necessary, and may also be used in combination with ultraviolet inhibitors, oxidation stabilizers, heat stabilizers, colorants, and mold release agents. It is also possible to contain appropriate amounts of additives such as plasticizers and various plasticizers.

The number average molecular weight of the copolymer according to the present invention determined by GPC is 7000 or more, preferably soo.

(iso)bornyl methacrylate and methacrylate which are particularly preferably used in the present invention. The glass transition temperature (TG) of the copolymer of the monomer mixture consisting of methyl acid, when the composition of the (iso)bornyl methacrylate monomer is X weight type, is the value represented by formula [2], or Since it has a value higher than that, it is possible to select a copolymer composition depending on the required heat resistance.

TGr°C)=0.60X-1-110 [2] where X indicates a value of 10 to 90.

The methacrylic copolymer based on the present invention can be used for construction materials,
It can be used in a wide range of fields, including signboards, signs, lighting equipment, furniture, industrial parts, arts and crafts, and daily necessities, as well as optical elements such as various lenses, prisms, concave mirrors, optical fibers, optical waveguides, and videos. It can also be used in discs, discs such as audio discs, covers for solar collectors that require heat resistance and water resistance, sanitary wear, glazing fields, etc.

〔Example〕

EXAMPLES The present invention will be specifically explained below using Examples, but the present invention is not limited thereto.

Example 1.2.3.4.5 and Comparative Examples A and B t-butyl 0.2 parts by weight of peroxyisobutyrate (selected for 10 hours, half-life temperature 78°C) was added, and a soft polyvinyl chloride pipe with an outer diameter of 6 mm (inner diameter of 4 mm) was used as a gasket.
After injecting into two reinforced glass mold cells measuring cyg x 30 cm, degassing was performed under reduced pressure, and the mixture was heated at 80°C for 6 hours.
Subsequently, polymerization was carried out by heating at 120° C. for 2 hours. The state of the obtained mold plate when it was released from the mold cell was observed, and it was cut into small pieces of about 5WIn square, dissolved in about 30 times the amount of benzene, and then
The mixture was poured into petroleum benzene of 00 times the volume with stirring to cause reprecipitation, which was then concentrated and dried. The residual monomer amount and glass transition temperature of the dried acrylic resin composition were measured and are shown in Table 1 along with comparative examples.

In the table, ◎ and ○ indicate good condition with no cracks on the surface of the cast plate (the degree of good is 0>O), and × indicates the condition at the time of release from the mold.
Indicates that cracks occurred during mold release.

The amount of residual monomer was determined by GPC measurement from the ratio of the area of the signal based on the obtained monomer component to the area of the entire signal.

The water absorption rate was determined from the weight increase rate when immersed in hot water at 90 to 95°C for 2 hours.

The glass transition temperature was determined by DSC measurement (heating rate 10°C/min).
) was obtained according to the conventional method.

As shown in Table 1, according to the present invention, no cracks occur in the cast plate after copolymerization, and the methacrylic resin composition has good heat resistance and water resistance as expressed by glass transition temperature and water absorption. You can get things.

Example 6.7.8 and Comparative Example C A monomer mixture consisting of 50% by weight of methyl methacrylate and 50% by weight of (iso)bornyl methacrylate monomer was treated with t-butylperoxyisobutyrate as a radical. It was added as a polymerization initiator, and cast polymerization was carried out using two reinforced glass cells in the same manner as in the previous example to obtain a cast plate.

The residual monomer content of the cast plate was 40% by weight (Comparative Example C). Next, the cast plate is cut into small pieces of about 5 square pieces, placed in about 30 times the volume of benzene, and taken out after a predetermined period of time to obtain a copolymer with a predetermined residual monomer content. A combination was obtained and the glass transition temperature was measured along with the comparative example. The results are shown in Table 2.

Table 2 As shown in Table 2, it can be seen that heat resistance is good if the residual monomer amount is based on the present invention.

Examples 9, 10 and Comparative Example D A radical polymerization initiator selected for 10 hours with a half-life temperature of 0.2 parts of lauroyl peroxide at 62°C, 0.3 parts by weight of luciferoxyisophthalate added at 107°C (D Schiff'), and cast polymerization was carried out using two tempered glass cells. A cast plate was obtained, and the residual monomer content and glass transition temperature were measured. [This is referred to as Example 9.] The number average molecular weight of this polymer by GPC was 44.0.
It was 00.

Next, this was cut into small pieces of about 5 mm square, then dissolved in benzene, poured into petroleum benzine, precipitated, filtered, and dried, and the remaining monomer amount and glass transition temperature were measured in the same way. . [This is referred to as Example 10. ] Also, for 100 parts by weight of the mixed monomer, t-butylperoxyisobutyrate (selected half-life temperature of 78°C for 10 hours)
) was added and cast polymerization was carried out in the same manner to obtain a cast plate.The remaining monomer amount and glass transition temperature were measured and shown in Table 3 as a comparative example. It was confirmed by NMR analysis that the obtained copolymer had the same composition as the charged monomer composition.

Note) *: Half-life temperature selected for 10 hours As shown in Table 3, methacrylic resins with excellent heat resistance and water resistance can be produced by using an initiator in combination with the present invention and by performing a reprecipitation operation. It turns out that it is possible to obtain the composition, but not by the methods as hitherto disclosed.

Furthermore, a disk-shaped molded product having a diameter of 301 and a thickness of 1.2 wgm was created by injection molding the three types of copolymers cut into small pieces. One side of this molded product has a thickness of 0.1 by vacuum deposition.
After forming a μm thick aluminum thin film and leaving it for 24 hours in an atmosphere with a temperature of 40°C and a relative humidity of 90%, the state of the molded product was observed.
, No. 10 showed no warping at all, and was confirmed to be effective as a disc material for video discs, audio discs, etc. On the other hand, in the comparative example, some warping occurred at 3 m, making it unsuitable for use as a disc material.

〔Effect of the invention〕

As described above in detail with reference to Examples, according to the present invention, a methacrylic copolymer having both heat resistance and water resistance can be obtained.

Claims (3)

[Claims] (1) Copolymerizing a monomer mixture consisting of 10 to 90% by weight of methyl methacrylate and 90 to 10% by weight of a methacrylic acid ester monomer having an alicyclic hydrocarbon group having 8 or more carbon atoms in the ester moiety. 1. A methacrylic copolymer obtained by using a methacrylic copolymer characterized in that the amount of residual monomer contained in the copolymer is 2.0% by weight or less. (2) 100 parts by weight of a monomer mixture consisting of 10 to 90% by weight of methyl methacrylate and 90 to 10% by weight of a methacrylic acid ester monomer having an alicyclic hydrocarbon group having 8 or more carbon atoms in the ester moiety When copolymerizing, 0.01 to 0.4 parts by weight of a radical polymerization initiator with a 10-hour half-life temperature of 45 to 80°C and 0.05 to 0.8 parts of a radical polymerization initiator with a half-life temperature of 90 to 110°C are used. A method for producing a methacrylic copolymer, characterized in that it is used in combination in parts by weight. (3) Copolymerization of a monomer mixture consisting of 10 to 90% by weight of methyl methacrylate and 90 to 10% by weight of a methacrylic acid ester monomer having an alicyclic hydrocarbon group having 8 or more carbon atoms in the ester moiety. The amount of residual monomer contained in the copolymer is reduced to 2.0% by weight or less by subjecting the resulting copolymer to a reprecipitation operation or an extraction operation. Method for producing methacrylic copolymer.