JP4507381B2 - Method for producing decrosslinked resin - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a crosslinkable composition, a crosslinkable resin obtained from the crosslinkable composition, and an easily recyclable decrosslinked resin obtained by heating the crosslinkable composition.
[0002]
[Prior art]
The cross-linked resin has an advantage that it is excellent in solvent resistance, heat resistance and the like as compared with a non-crosslinked thermoplastic resin. For example, methacrylic resins are excellent in transparency and weather resistance, so they are used in the fields of lighting materials, optical materials, displays, decorative members, building materials, greenhouse corrugated plates, artificial marble, etc. In order to improve the solvent resistance and heat resistance of the resin, it is known that the methacrylic resin is a cross-linked type.
As a method for producing a cross-linked resin, there is a method in which a vinyl monomer such as styrene or methyl methacrylate is used as a cross-linking agent using a di (meth) acrylate such as diethylene glycol di (meth) acrylate as a cross-linking agent. Are known.
[0003]
For example, in Polymer Chemistry, Vol. 27, No. 297, p65, 1970, in the polymerization of methyl methacrylate and styrene, ethylene glycol derivatives such as diethylene glycol dimethacrylate and tetraethylene glycol dimethacrylate were used as crosslinking agents. A method for producing a cross-linked resin using dimethacrylate having the resulting ester is disclosed.
[0004]
Japanese Patent Application Laid-Open No. 57-167340 discloses a linear chain such as 1,6-hexanediol di (meth) acrylate as a cross-linking agent in the polymerization of a vinyl monomer mainly composed of methyl methacrylate. Discloses a method for producing a cross-linked resin using di (meth) acrylate having an ester derived from an alkanediol having a shape.
[0005]
In recent years, resin recycling has become an important issue from the viewpoint of conservation of the global environment and effective use of resources. However, since the cross-linkable resin obtained using the cross-linking agent disclosed in the prior art is insoluble and infusible and difficult to de-crosslink by heating, it is effectively treated or reused after use. It was difficult to do.
[0006]
[Problems to be solved by the invention]
The present invention has been made paying attention to the problems that exist in the prior art. The object is to provide a crosslinkable composition, a crosslinkable resin obtained from the crosslinkable composition, and an easily recyclable decrosslinked resin obtained by heating the crosslinkable composition.
[0007]
[Means for Solving the Problems]
As a result of diligent studies to achieve the above object, the present inventors can easily obtain a crosslinkable resin by using di (meth) acrylate having an ester bond derived from a tertiary alcohol as a crosslinker, And it discovered that it could de-crosslink easily by heating it, and completed this invention.
[0008]
That is, the present invention provides a crosslinked resin obtained by polymerizing and crosslinking a crosslinkable composition comprising a vinyl monomer, a di (meth) acrylate represented by the formula (1), and a radical generator. It is a method for producing a decrosslinked resin in which the ester bond caused by the tertiary alcohol contained in the crosslinkable resin is cleaved and decrosslinked.
[0009]
[Chemical 2]
(Wherein R ¹ Is a hydrogen atom or a methyl group, R ² Represents a linear or branched alkylene group having 1 to 11 carbon atoms. )
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail.
The vinyl monomer used in the present invention is a radically polymerizable ethylenically unsaturated compound, such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, etc. Methacrylic acid esters; acrylic acid esters such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate; unsaturated such as acrylic acid, methacrylic acid, maleic acid, itaconic acid Carboxylic acid; Acid anhydrides such as maleic anhydride and itaconic anhydride; 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate , Tetrahydrofurfuryl acrylate, monoglycerol acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, tetrahydrofurfuryl methacrylate, monoglycerol methacrylate and other hydroxyl group-containing monomers; acrylamide, methacrylamide, N-phenylmaleimide , Acrylonitrile, methacrylonitrile, diacetone acrylamide, dimethylaminoethyl methacrylate and other nitrogen-containing monomers; allyl glycidyl ether, glycidyl acrylate, glycidyl methacrylate and other epoxy group-containing monomers; polyethylene glycol monomethacrylate, polypropylene glycol monomethacrylate , Alkylene such as polyethylene glycol monoallyl ether Monomer containing monomer: Styrene monomer such as styrene, α-methylstyrene, p-methylstyrene, chlorostyrene, t-butylstyrene; vinyl acetate, vinyl propionate, vinyl caproate, vinyl caprylate, laurin Examples thereof include vinyl esters such as vinyl acid and vinyl stearate; vinyl chloride, vinylidene chloride, vinylidene fluoride, and ethylene.
In addition, these can be used individually or in combination of 2 or more types.
[0013]
Among these, monomers having a methyl methacrylate as a main component are preferable because the monomer reactivity is similar to that of the crosslinking agent of the present invention and a relatively uniform network structure can be provided. That is, it is a vinyl monomer mixture composed of methyl methacrylate alone or methyl methacrylate and a monomer copolymerizable therewith, and the vinyl monomer mixture contains 50% by weight or more of methyl methacrylate. As the monomer copolymerizable with methyl methacrylate, one or more kinds are selected from the vinyl monomers.
[0014]
In the present invention, in order to increase the viscosity of the crosslinkable composition and improve the moldability, it is preferable to further include a polymer of the monomer in the vinyl monomer. The monomer solution containing a vinyl monomer polymer is usually called a syrup, and is obtained by dissolving a vinyl monomer polymer in the monomer or by polymerizing a vinyl monomer. Can be prepared by proceeding to a certain extent.
[0015]
The weight average molecular weight of the vinyl monomer polymer in the syrup is usually 5,000 to 2,000,000, preferably 10,000 to 1,000,000, and the content is usually 60% by weight or less, preferably 50% by weight or less. . If the weight average molecular weight exceeds 2000000 or the content exceeds 60% by weight, the syrup viscosity tends to be too high and handling tends to be difficult.
[0016]
The di (meth) acrylate having a specific structure used in the present invention is a structure represented by the general formula (1) and is a di (meth) acrylate having an ester bond derived from a tertiary alcohol. A cross-linked body is formed by copolymerization with the vinyl monomer and acts as a cross-linking agent.
In the formula (1), R ² Represents a linear or branched alkylene group having 1 to 11 carbon atoms. Depending on the mode of branching, esters derived from primary and tertiary alcohols, esters derived from secondary and tertiary alcohols, two tertiary The structure has an ester derived from alcohol.
[0017]
Specific examples of the compound represented by the formula (1) include 2-methyl-1,2-propanediol diacrylate, 2-methyl-1,2-propanediol dimethacrylate, 3-methyl-1,3- Di (meth) acrylates having esters derived from primary and tertiary alcohols such as butanediol diacrylate, 3-methyl-1,3-butanediol dimethacrylate; 2-methyl-2,4-pentanediol diacrylate; Di (meth) acrylates having esters derived from secondary and tertiary alcohols such as 2-methyl-2,4-pentanediol dimethacrylate; 2,3-dimethyl-2,3-butanediol diacrylate, 2,3 -Dimethyl-2,3-butanediol dimethacrylate, 2,4-dimethyl-2,4-pentanediol diac Relate, 2,4-dimethyl-2,4-pentanediol dimethacrylate, 2,5-dimethyl-2,5-hexanediol diacrylate, 2,5-dimethyl-2,5-hexanediol dimethacrylate, 2,7 -Dimethyl-2,7-octanediol diacrylate, 2,7-dimethyl-2,7-octanediol dimethacrylate, 2,9-dimethyl-2,9-decanediol diacrylate, 2,9-dimethyl-2, It has esters derived from two tertiary alcohols such as 9-decanediol dimethacrylate, 2,11-dimethyl-2,11-dodecanediol diacrylate, 2,11-dimethyl-2,11-dodecanediol dimethacrylate, etc. Examples include di (meth) acrylate.
[0018]
In particular, 2-methyl-2,4-pentanediol diacrylate, 2-methyl-2,4-pentanediol dimethacrylate, 2,5-dimethyl-2,5-hexanediol diacrylate, 2,5-dimethyl-2 , 5-hexanediol dimethacrylate is preferred because the crosslinking and decrosslinking reactions proceed efficiently.
[0019]
The di (meth) acrylate can be produced according to a general method for producing a conventional (meth) acrylate. For example, it can be obtained by subjecting (meth) acrylic acid chloride and the corresponding diol to an esterification reaction in the presence of a base such as triethylamine.
[0020]
The amount of the di (meth) acrylate used is usually 0.5 to 100 parts by weight, preferably 1 to 80 parts by weight, based on 100 parts by weight of the vinyl monomer, although it varies depending on the desired degree of crosslinking. If it is less than 0.5 part by weight, crosslinking does not proceed effectively. Moreover, when it exceeds 100 weight part, it exists in the tendency for physical properties, such as the intensity | strength of crosslinked resin, to fall.
[0021]
The radical generator used in the present invention is a compound that generates radicals effectively by radical decomposition by heat or light.
For example, dialkyl peroxides such as di-t-butyl peroxide, di-t-hexyl peroxide and dicumyl peroxide; 1,1-bis (t-butylperoxy) cyclohexane, 1,1-bis (t-butylperoxy)- Peroxyketals such as 3,3,5-trimethylcyclohexane and 2,2-bis (4,4-di-t-butylperoxycyclohexyl) propane; t-butylperoxybenzoate, t-hexylperoxybenzoate, t-butylperoxy Acetate, t-butylperoxylaurate, t-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxyisobutyrate, t-butylperoxy-2-ethylhexanoate, t-hexylperoxy- 2-ethylhexanoate Peroxyesters such as t-butylperoxypivalate, t-hexylperoxypivalate, t-butylperoxyneodecanoate, t-hexylperoxyneodecanoate, cumylperoxyneodecanoate; t-butylperoxyisopropyl Monoperoxycarbonates such as monocarbonate, t-hexylperoxyisopropyl monocarbonate, t-butylperoxy-2-ethylhexyl monocarbonate; diacyl peroxides such as benzoyl peroxide, lauroyl peroxide, 3,5,5-trimethylhexanoyl peroxide; Peroxy dicarbonates such as di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (2,4-dimethyl-4-methoxyvaleronitrile) Azo compounds such as 1,1′-azobis (cyclohexanecarbonitrile), 2,2′-azobis (2,4,4-trimethylpentane); benzophenone, 4-phenylbenzophenone, xanthone, thioxanthone, 2-chlorothioxanthone, 4,4′-bis (N, N′-dimethylamino) benzophenone, benzyl, 9,10-phenanthraquinone, 9,10-anthraquinone, α, α-dimethyl-α-hydroxyacetophenone, 1-hydroxycyclohexylphenyl Ketone, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether , Benzoin isobutyl ether, α, α-dimethoxy-α-phenylacetophenone, α, α-diethoxyacetophenone, 1-phenyl-1,2-propanedione-2- (O-benzoyl) oxime, diphenyl (2,4, 6-trimethylbenzoyl) phosphine oxide, α-dimethylamino-α-ethyl-α-benzyl-3,5-dimethyl-4-morpholinoacetophenone, 3,3 ′, 4,4′-tetra (t-butylperoxycarbonyl) Examples include photoinitiators such as benzophenone.
[0022]
These radical generators can be used alone or in combination of two or more. In order to accelerate the reaction, an accelerator such as cobalt naphthenate and dimethylaniline can be used in combination.
Among these radical generators, thermal decomposition type radical generators such as peroxides and azo compounds are preferable because the radical generation rate can be easily controlled.
[0023]
The amount of these radical generators used is usually 0.001 to 10 parts by weight, preferably 0.01 to 5 parts by weight, based on 100 parts by weight of the monomer. If it is less than 0.001 part by weight, the polymerization rate tends to be slow and the residual amount of monomer tends to increase. On the other hand, if it exceeds 10 parts by weight, it tends to be difficult to adjust the polymerization rate.
[0024]
The crosslinkable resin of the present invention can be obtained by polymerizing / crosslinking the crosslinkable composition.
Polymerization / crosslinking means that a crosslinking reaction proceeds simultaneously with a polymerization reaction by copolymerization of a vinyl monomer and the crosslinking agent. The cross-linked resin of the present invention thus obtained has a structure in which an ester bond derived from a tertiary alcohol is introduced into a cross-linked site.
As a polymerization / crosslinking method, the crosslinkable composition may be heated or irradiated with ultraviolet light so that the radical generator effectively generates radicals. In particular, the method by heating in the presence of a pyrolytic radical generator is preferable in that it can be easily performed.
[0025]
The heating temperature is a temperature at which the aforementioned radical generator decomposes at an appropriate rate, and is usually 50 to 150 ° C, preferably 60 to 140 ° C. If it is less than 50 ° C., the polymerization rate tends to be slow and the residual amount of monomer tends to increase. On the other hand, if it exceeds 150 ° C., the polymerization rate tends to be difficult to adjust.
[0026]
In the present invention, for example, n-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, 2-ethylhexyl-β-mercaptopro is used to adjust the polymerization degree of the crosslinkable resin and the polymerization rate of the vinyl monomer. Chain transfer agents such as pionate and α-methylstyrene dimer can be used.
[0027]
Further, depending on the application, the crosslinkable composition may be made of a reinforcing material such as glass fiber, vinylon fiber, or carbon fiber, an inorganic filler such as calcium carbonate, aluminum hydroxide, or clay, a release agent, an ultraviolet absorber, a colorant, or a stabilizer. Additives such as flame retardants may be mixed.
[0028]
When the cross-linked resin is produced in the present invention, various molded products can be obtained by simultaneously performing the molding. As the molding method, all known molding methods that are usually performed on thermosetting resins are applicable. For example, cast molding method, compression molding method, transfer molding method, injection molding method, extrusion molding method, etc. Is mentioned.
Formed articles such as methacrylic plates, artificial marble for bathtubs and kitchen products can be obtained by the above molding means.
[0029]
The decrosslinked resin of the present invention is an easily recyclable resin obtained by heat-cutting an ester bond caused by a tertiary alcohol contained in the crosslinked resin obtained as described above.
Since the ester bond caused by the tertiary alcohol is usually lower than the decomposition temperature of the resin body, the bond can be selectively cut by heating at an appropriate temperature. Although heating temperature is suitably selected by the kind of di (meth) acrylate shown to the formula (1) used, the kind of resin main body, etc., it is normally 180-300 degreeC temperature, Preferably it is 200-280 degreeC. When the heating temperature is less than 180 ° C., cleavage of the ester bond caused by the tertiary alcohol does not occur or tends to not proceed efficiently. Moreover, when it exceeds 300 degreeC, it exists in the tendency for decomposition | disassembly of resin main bodies, such as depolymerization, to occur easily, and the reproduction | regeneration as resin becomes difficult.
[0030]
In the present invention, decrosslinking does not necessarily include complete decrosslinking, but also includes partial decrosslinking. The degree of decrosslinking is adjusted by the heating temperature and heating time, and optimal conditions are selected.
When the degree of decrosslinking is desired to be relatively small, decrosslinking under mild conditions, that is, heat treatment at a relatively low temperature within the above heating temperature range, or heat treatment in a short time even at a high temperature. do it.
[0031]
The heating method is not particularly limited, and examples thereof include heating in an oven, heating under pressure by a press, and heating while kneading. In addition, when a partially decrosslinked resin is required, it can be easily obtained by selecting conditions for heating only a part of the crosslinked resin.
[0032]
The decrosslinked resin obtained by the above-described method can be reused as a molding material and can be used for various applications depending on the degree of decrosslinking.
For example, almost completely decrosslinked resin can be formed into various molded products by molding methods usually performed with thermoplastic resins, such as injection molding, extrusion molding, blow molding and the like. At that time, another thermoplastic resin can be mixed and molded.
On the other hand, a resin having a relatively low degree of decrosslinking can be melt-kneaded with other thermoplastic resins and finely dispersed in a thermoplastic resin matrix to form various molded products.
It is also possible to remove the cross-linked resin by partially heating and removing only the de-cross-linked portion by solvent washing or processing.
[0033]
【Example】
Next, the present invention will be described more specifically with reference to examples and comparative examples. In addition, unless otherwise indicated, the part and% in each example show a weight part and weight%. Moreover, the symbol in each example represents the following compounds.
25DMA and HGDMA were synthesized by the methods of Reference Example 1 and Reference Example 2, and 25DA was synthesized according to the method described in JP-A-9-52864.
[0034]
Abbreviations indicate the following meanings.
25DMA: 2,5-dimethyl-2,5-hexanediol dimethacrylate,
HGDMA: 2-methyl-2,4-pentanediol dimethacrylate,
25DA: 2,5-dimethyl-2,5-hexanediol diacrylate,
DEGDMA: Diethylene glycol dimethacrylate,
MMA: methyl methacrylate.
[0035]
Reference example 1
A 200 ml four-necked flask equipped with a stirrer and a thermometer is charged with 5 g of 2,5-dimethyl-2,5-hexanediol, 10.4 g of triethylamine and 50 ml of methylene chloride, and is stirred at 15 ° C. in a water bath. Kept. Thereto, 10.8 g of methacrylic acid chloride was dropped over 15 minutes. Stirring was continued for 4 hours at the temperature of 15-20 degreeC after completion | finish of dripping.
[0036]
After completion of the reaction, 100 ml of n-hexane and 100 ml of 5% aqueous hydrochloric acid were added, and the organic layer was separated. The organic layer was washed with 5% sodium hydroxide aqueous solution, 5% hydrochloric acid aqueous solution, saturated sodium hydrogen carbonate aqueous solution and water in this order. After dehydrating the organic layer with anhydrous magnesium sulfate, the solvent was distilled off under reduced pressure to obtain 8.79 g of a crude product.
This was purified by a silica gel column to obtain a colorless transparent liquid. Its infrared absorption spectrum (IR) and nuclear magnetic resonance spectrum ( ¹ 1 H-NMR) confirmed that the resulting compound was 25DMA.
[0037]
Reference example 2
A 200 ml four-necked flask equipped with a stirrer and a thermometer was charged with 5 g of 2-methyl-2,4-pentanediol, 12.9 g of triethylamine and 50 ml of methylene chloride, and kept at 15 ° C. in a water bath with stirring. . Thereto, 13.3 g of methacrylic acid chloride was dropped over 15 minutes. Stirring was continued for 4 hours at the temperature of 15-20 degreeC after completion | finish of dripping.
After completion of the reaction, water was added to separate the solution, and the organic layer was washed with 5% aqueous sodium hydroxide, 5% aqueous hydrochloric acid and water. After the organic layer was dehydrated with anhydrous magnesium sulfate, the solvent was distilled off under reduced pressure to obtain 9.75 g of a crude product. This was purified by a silica gel column to obtain a colorless transparent liquid.
Infrared absorption spectrum (IR) and nuclear magnetic resonance spectrum of the obtained compound ( ¹ 1 H-NMR) confirmed that the obtained compound was HGDMA.
[0038]
Example 1
A mixed solution containing 95 parts of styrene, 5 parts of 25DMA and 0.1 part by weight of t-butylperoxybenzoate as a polymerization initiator with respect to styrene is placed in a glass ampule, sealed with nitrogen, sealed in a thermostatic bath at 120 ° C, Polymerization was carried out for 5 hours to obtain a polymer.
A sample of about 0.1 g was collected from this polymer and immersed in 10 ml of benzene at room temperature overnight. As a result, the sample became a swollen gel. Furthermore, as a result of obtaining the dissolution rate according to the following formula, the dissolution rate was 10% or less. From this, it was confirmed that this polymer has a crosslinked structure and is excellent in solvent resistance.
[0039]
[Expression 1]
[0040]
Next, a sample of about 0.1 g was separately taken from the polymer, heated in an oven at 250 ° C. for 30 minutes, and then subjected to the same solubility test as described above. As a result, the dissolution rate of the sample after heating was 100% and was completely dissolved in benzene.
About the sample after a heating, tetrahydrofuran (THF) was used as a solvent, and the molecular weight was measured by the gel permeation chromatography (GPC) using the calibration curve by a standard polystyrene. As a result, the weight average molecular weight was 316,000.
[0041]
Comparative Example 1
Polymerization was carried out in the same manner as in Example 1 except that 25DMA was not used. The obtained polymer was examined for solubility in benzene according to Example 1. As a result, the dissolution rate was 100%, and the polymer was completely dissolved in benzene. Moreover, the weight average molecular weight calculated | required by GPC was 317,000.
[0042]
Comparative Example 2
The test was conducted in the same manner as in Example 1 except that DEGDMA was used instead of 25DMA. As a result, the dissolution rate was 10% or less for both the sample before and after heating at 250 ° C.
[0043]
Example 2
A mixed solution containing 98 parts of MMA, 2 parts of 25 DMA, 0.21 parts by weight of lauroyl peroxide as a polymerization initiator with respect to MMA and 0.3% of n-dodecyl mercaptan as a chain transfer agent (% by weight with respect to the volume of the entire solution) is made of glass. It was put into an ampule, sealed with nitrogen, sealed in a constant temperature bath at 70 ° C., and polymerized for 5 hours to obtain a polymer.
[0044]
A sample of about 0.1 g was taken from this polymer and immersed in 10 ml of benzene at 40 ° C. overnight, resulting in a swollen gel. Furthermore, as a result of obtaining the dissolution rate according to the above formula, the dissolution rate was 10% or less. From this, it was confirmed that this polymer has a crosslinked structure and is excellent in solvent resistance.
[0045]
Next, a sample of about 0.1 g was separately taken from the polymer, heated in an oven at 250 ° C. for 30 minutes, and then subjected to the same solubility test as described above. As a result, the sample had a dissolution rate of 100% after heating and was completely dissolved in benzene.
About the sample after a heating, tetrahydrofuran (THF) was used as a solvent, and the molecular weight was measured by the gel permeation chromatography (GPC) using the calibration curve by a standard polystyrene. The results are shown in Table 1.
[0046]
[Table 1]
[0047]
The abbreviations in the table indicate the following.
25DMA: 2,5-dimethyl-2,5-hexanediol dimethacrylate, HGDMA: 2-methyl-2,4-pentanediol dimethacrylate,
25DA: 2,5-dimethyl-2,5-hexanediol diacrylate,
DEGDMA: Diethylene glycol dimethacrylate,
MMA: methyl methacrylate.
[0048]
Examples 3-6, Comparative Examples 3-4
A sample was produced in the same manner as in Example 2 except that the type and addition amount of the crosslinking agent in Example 2 were as described in Table 1, and the dissolution rate and heating of the sample in benzene before and after heating at 250 ° C. The molecular weight of the post sample was determined. The results are shown in Table 1. In the case of Comparative Example 4, the sample after heating did not dissolve in THF, so the molecular weight could not be measured.
[0049]
Example 7
In Example 2, the test was performed in the same manner except that the heating temperature of the oven was 200 ° C. As a result of obtaining the dissolution rate of the sample after heating, the dissolution rate was 86%. Although it was not completely dissolved in benzene, an improvement in the dissolution rate due to partial decrosslinking was observed.
[0050]
Example 8
100 parts of MMA syrup with a viscosity of 10 poise at 20 ° C. and a polymerization rate of 20%, 1 part of methyl acrylate, 5 parts of 25 DMA, 0.1 part of n-dodecyl mercaptan, 0.3 part of t-hexyl peroxypivalate and a small amount of release The mold was added and dissolved, followed by vacuum degassing. This was poured into a casting cell made of two glass plates and a polyvinyl chloride gasket, held in a 70 ° C. water bath for 8 hours, and then polymerized in a 120 ° C. air bath for 2 hours to obtain a thickness. A 3 mm resin plate was obtained.
[0051]
A sample was collected from the obtained resin plate and the dissolution rate was determined by the method of Example 2. As a result, the dissolution rate was 10% or less, and it was found that the obtained resin plate was excellent in solvent resistance.
Next, a sample was separately taken from the resin plate and heated in an oven at 250 ° C. for 30 minutes, and then the dissolution rate was determined in the same manner as described above. As a result, the dissolution rate was 100% and was completely dissolved in benzene.
[0052]
Comparative Example 5
The test was performed in the same manner as in Example 7 except that DEGDMA was used instead of 25DMA. The dissolution rate was 10% or less for both the samples before and after heating at 250 ° C.
[0053]
From the solubility test of the polymer before heating in Example 1 and Comparative Example 2, the crosslinking agent contained in the crosslinking composition of the present invention functions effectively as a crosslinking agent during styrene polymerization as in conventional DEGDMA. It was found that a cross-linked resin having excellent solvent resistance was obtained.
Further, from the solubility test of the polymer after heating in Example 1 and Comparative Example 2, the conventional crosslinkable resin remained insoluble in the solvent even when heated, but the crosslinkable resin of the present invention was heated to the solvent. It was found to be soluble.
In addition, as is apparent from the GPC measurement results of Example 1 and Comparative Example 1, what is obtained after the heating is substantially the same in molecular weight as polystyrene obtained without using a cross-linking agent. As a result of selective cleavage of the ester bond caused by the tertiary alcohol contained in the site, it was found that the polymer was decrosslinked to become a linear polymer.
That is, it became clear that the crosslinkable resin of the present invention can be converted into a thermoplastic resin that can be easily reshaped by simply heating.
[0054]
From the results of Examples 2 to 6 and Comparative Examples 3 to 4, the same fact as in the case of styrene was observed when MMA was used as the vinyl monomer.
As is clear from the results of Example 7, it was found that partial decrosslinking was possible by heating at a relatively low temperature.
Further, as is clear from the comparison between Example 8 and Comparative Example 5, the molded body obtained by using the crosslinking agent of the present invention was also heated for the molded body obtained by heat molding after pouring into the mold. It was found that it can be easily decrosslinked.
[0055]
【The invention's effect】
As described above in detail, the crosslinkable composition of the present invention contains a vinyl monomer and a di (meth) acrylate type crosslinker excellent in radical copolymerization, and thus has excellent solvent resistance. A cross-linked resin can be easily obtained.
In addition to the above properties, the crosslinkable resin of the present invention is provided with an ester bond due to a tertiary alcohol derived from a crosslinker that decomposes at a temperature lower than the decomposition temperature of the resin main body at the crosslink site. Can be decrosslinked without decomposing.
The decrosslinked resin thus obtained can be used as various molded articles by injection molding, extrusion molding, blow molding or the like. The crosslinked resin can be partially heated to remove only the decrosslinked portion by solvent cleaning or processing.
Further, the present invention is extremely valuable in that the cross-linked resin can be effectively treated or reused after use.

Claims (1)

A crosslinked resin obtained by polymerizing and crosslinking a crosslinkable composition comprising a vinyl monomer, a di (meth) acrylate represented by the formula (1) and a radical generator is heated at 180 ° C. to 300 ° C. for crosslinking. A method for producing a decrosslinked resin in which an ester bond caused by a tertiary alcohol contained in a mold resin is cleaved and decrosslinked.
(In the formula, R ¹ represents a hydrogen atom or a methyl group, and R ² represents a linear or branched alkylene group having 1 to 11 carbon atoms.)