JPS6244566B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a styrenic polymer having a bicycloorthoester group introduced into its side chain. Generally, it is well known that monomers such as ethylenically unsaturated compounds undergo considerable volume shrinkage during homopolymerization and copolymerization; for example, the volume shrinkage rates during polymerization of ethylene, acrylonitrile, methyl methacrylate, and styrene are 66.0%, 31.0%,
21.2% and 14.5%. If the volume shrinkage during polymerization is large, for example, when used as a molding material, dimensional accuracy may be lost, when used as a casting material, the cast product may be distorted due to shrinkage, or the adhesive force with the mold may be reduced. There are problems such as gaps being created. In addition, when used as a paint, internal distortion may cause a decrease in adhesion to the coated plate and cause warping, and when used as an adhesive, internal distortion may cause a decrease in adhesive strength, warpage, deformation, etc. cause problems. Furthermore, it is also known that common crosslinkable polymers shrink when crosslinked and cured. Epoxy resins have a low shrinkage rate during crosslinking and curing due to ring opening of epoxy groups, so they are widely used in paints, adhesives, molded products that require dimensional accuracy, cast products, etc.
The shrinkage rate of epoxy resin varies somewhat depending on the type of crosslinking agent, curing time and temperature, but is about 1 to several percent (see Kobunshi, Vol. 27, February issue, 1978, pp. 108-111). Substances that do not substantially shrink or preferably expand upon polymerization of monomers or crosslinking of polymers are currently highly sought after as materials for the construction of sophisticated devices, such as strain-free composites, adhesives, and casting materials. It is valued and explored. As a result of repeated research aimed at developing a styrenic polymer that does not show shrinkage during crosslinking, the present inventors found that by introducing a specific bicycloorthoester group into the benzene nucleus of the styrene unit, a styrenic polymer can be obtained. The present invention was completed based on the finding that the combination does not substantially cause contraction during crosslinking due to ring opening of the orthoester group, but on the contrary can expand by about 1 to 3%. Thus, the present invention provides the following formula: (wherein A represents a monomer unit composed of at least one ethylenically unsaturated compound, and R
represents a lower alkyl group, and x and y represent the mole fraction of each structural unit. ), and the ratio of x and y is y/(x+y)=1/100
-99/100 and a polystyrene equivalent weight average molecular weight of 1,000 to 600,000. In formula (), R represents a lower alkyl group such as a methyl group, an ethyl group, a propyl group or a butyl group. Monomer unit A in formula () is derived from at least one type of styrene and known ethylenically unsaturated compounds that can be copolymerized with styrene, and specific examples of such ethylenically unsaturated compounds include the following: Examples include compounds. Esters of acrylic and methacrylic acids, such as methyl, ethyl, propyl, butyl esters of acrylic and methacrylic acids; substituted styrenes, such as divinylbenzene, o-, m- or p
- Chlorstyrene, m- or p-chloromethylstyrene, α-methylstyrene, p-methoxystyrene, p-dimethylaminostyrene, p-cyanostyrene, p-nitrostyrene, α-acetoxystyrene, etc.; ethylene, 1,2 -Dichloroethylene, isobutylene, butadiene, isoprene, chloroprene; vinyl chloride, vinyl acetate, vinylidene chloride, allyl chloride, allyl acetate; methyl vinyl ether, ethyl vinyl ether; ethyl vinyl ketone, vinylene carbonate, isopropyl vinyl ketone; N-vinylpyrrolidone, 2-vinylpyridine, 5-methyl-2-vinylpyridine; acrylonitrile, methacrylonitrile; methyl cinnamate, ethyl cinnamate, vinyl cinnamate, nitrile cinnamate; vinyl benzoate, allyl benzoate; acrylic acid , methacrylic acid, maleic acid, and other unsaturated carboxylic anhydrides, such as maleic anhydride, itaconic anhydride, citraconic anhydride, and the like. Preferred ethylenically unsaturated compounds have the following formula: (In the formula, R ₁ is hydrogen or an alkyl group, and R ₂
is a compound represented by -CN, _-COOR3 , _-OCOR3 , phenyl or a phenyl group having alkyl, halogen or haloalkyl as a substituent, and _R3 is an alkyl group). The styrenic polymer consisting of the structural unit of the formula () according to the present invention is generally produced by adding a styrene homopolymer or copolymer having a chloromethyl group to the benzene nucleus of the styrene according to the reaction formula below. It can be produced by a dechlorination sodium reaction using an orthoester compound. The above reaction may be carried out in a suitable organic solvent such as tetrahydrofuran, dimethyl sulfoxide or usually dimethylformamide (DMF) at a temperature of about 20 DEG to 100 DEG C. A styrenic polymer having a chloromethyl group in the benzene nucleus of styrene can be produced by (a) introducing a chloromethyl group into the benzene nucleus of the styrene polymer;
(b) It can be obtained by polymerizing a chloromethylstyrene monomer or copolymerizing it with another ethylenically unsaturated compound to incorporate a chloromethyl group into the polymer. The chloromethylation method in (a) above includes (i) a method in which formaldehyde and hydrogen chloride are applied to a styrene polymer in the presence of zinc chloride (Yoshiro Ogata, "New Edition of Organic Reactions", 1962, No. 200). (see page 201), (ii) styrenic polymer with formaldehyde,
(iii) A method in which chloromethyl ether (ClCH ₂ OCH ₃ ) is reacted on a styrene polymer in the presence of a Friedel-Crafts catalyst, such as zinc chloride (Polymer Science Society of Japan Polymer Experiments) (See “Polymer Reactions” edited by the Academic Editorial Committee, Polymer Experimental Studies 6, 1978, pp. 52-53). Normal method (iii) is appropriate, and according to this method,
For example, a styrene polymer is dissolved in chloromethyl ether, anhydrous zinc chloride is added as a catalyst, and the mixture is heated to 25°C.
React at ~45°C. Immediately after the reaction was completed, a methanol:dioxane (1:1) solution was added to stop the reaction, and then the reaction solution was mixed with methanol:water (7:1).
3) Pour into solution to precipitate the product. The obtained solid is dissolved in, for example, dioxane or methylene chloride, and purified by reprecipitation with methanol to obtain a chloromethylated product. According to the chloromethyl group introduction method described in (a) above, a bicycloorthoester group can be easily introduced into commercially available monodisperse polystyrene, and monodisperse polystyrene has a uniform molecular weight distribution and therefore has physical properties. A certain bicycloorthoester group-containing styrenic polymer is obtained. The method (b) above can be carried out by known radical polymerization, ionic polymerization, or radiation polymerization, which are commonly employed in the polymerization of vinyl monomers. The chloromethylated polymer produced by the method (a) or (b) above is prepared by dissolving a solution of the chloromethylated polymer in a solvent in which the produced polymer is soluble, such as methylene chloride, dioxane, dimethylformamide, etc.
- Separation and purification can be achieved by repeating several times the operation of adding the copolymer dropwise to a precipitation solvent such as hexane or methanol under stirring to precipitate the copolymer. The sodium alkoxide of the above formula () is
The following formula: 1-alkyl-4-hydroxymethyl-2,
It is obtained by reacting 6,7-trioxabicyclo[2,2,2]octane with sodium hydride in a tetrahydrofuran solvent, for example. The compound of the formula () is described in the specification of Japanese Patent Application No. 11432/1987 filed by the present applicant, and is a compound of pentaerythritol and the formula: R-C(OR') ₃ (R' is an alkyl group) with trialkyl orthoacylate. In the styrenic polymer of formula () according to the present invention, if the monomer unit having a bicycloorthoester group is present in the polymer in an amount of about 1 mol%, the volume shrinkage during crosslinking can be substantially improved. , molar ratio y/x+ of monomer units in the above formula ()
It can be present in any proportion where y is in the range of 1/100 to 99/100. However, the presence of more than 50 mol% of bicycloorthoester units not only increases costs but also leads to a decrease in water resistance.
Preferably, the y/x+y ratio is in the range of about 3/100 to 50/100. In addition, the molecular weight of the styrene-based polymer of the present invention represented by the above formula () is, as described above, a styrene homopolymer or copolymer having a chloromethyl group in the benzene nucleus of styrene. The molecular weight of the polymer of the present invention is determined by the weight average molecular weight in terms of polystyrene.
1000-600000. Since the polymer of the present invention has a volume-expanding bicycloorthoester group in the molecule, it exhibits the property of substantially expanding its volume upon crosslinking and curing.
In addition, crosslinking improves physical properties such as heat resistance and solvent resistance. Thus, the polymer of the present invention eliminates the above-mentioned drawbacks associated with volumetric shrinkage, and can be used as a paint with good adhesion that does not cause voids, an adhesive that does not cause internal distortion,
It is extremely useful for manufacturing composite materials, cast materials, etc. that require dimensional accuracy. For example, it is possible to obtain an excellent coating film by dissolving the polymer of the present invention in an appropriate solvent and applying it to the substrate surface, and then curing the formed coating film by an appropriate crosslinking means. After injection, it can be crosslinked to obtain an improved molded article. The polymer of the present invention undergoes crosslinking according to a cationic polymerization mechanism, and has bicycloorthoester groups.

A crosslinked polymer is formed by the ring-opening polymerization reaction of [Formula]. This crosslinking is usually initiated using a cationic polymerization catalyst. Examples of cationic polymerization catalysts used for this purpose include BF ₃ , FeCl ₃ ,
Lewis acids such as SnCl ₄ , SbCl ₃ , SbF ₃ , TiCl ₄ ;
BF ₃ OEt ₂ , BF ₃ - Coordination compounds of Lewis acids such as aniline complexes and compounds containing O, S, N, etc.; oxonium salts, diazonium salts, carbonium salts, halogen compounds of Lewis acids,
Examples include mixed halogen compounds and perhalogen acid derivatives. The amount of catalyst used is generally in the range of 0.001 to 10% by weight based on the polymer to be crosslinked. Although there are no particular restrictions regarding the polymerization temperature, it is usually carried out at room temperature to 200°C. Further, crosslinking can also be carried out by irradiation with radiation such as electron beams and ultraviolet rays. In the case of ultraviolet irradiation, as a cationic polymerization catalyst, for example, aromatic diazonium salts such as φ-N≡N・PF6, φ-N≡N・BF4; aromatic halonium salts such as φ-I ⁺ −φ・BF4; Aromatic onium salts of Group Va elements of the periodic table, such as:

Aromatic onium salts of elements of group a of the periodic table, such as: ##STR1## may be used. Next, the present invention will be further explained by reference examples and examples. Reference Example 1 (Production of chloromethylated polystyrene [A]) 5 g of polystyrene (weight average molecular weight 330,000) and 90 ml of chloromethyl ether were charged into a 4-necked 300 ml flask equipped with a stirring bar, condenser, dropping funnel, and thermometer. 30 minutes until a homogeneous solution is obtained.
Stir at ℃. Next, 0.9 g of anhydrous zinc chloride was added and stirred, and the reaction solution turned purple. After reacting for about 11 minutes, 30 ml of methanol:dioxane (1:1) solution was added to stop the reaction. The obtained reaction solution was poured into 500 ml of methanol:water (7:3) solution to precipitate the product. The produced white solid was washed with water and then with methanol. Next, it was dissolved in 50 ml of dioxane, purified by precipitation with methanol, further dissolved in 50 ml of methylene chloride, and purified by reprecipitation with methanol to obtain 5.1 g of chloromethylated polystyrene. Through nuclear magnetic resonance spectroscopy (NMR) analysis,
It was observed that 0.18 chloromethyl groups were introduced per benzene ring. Reference Example 2 (Manufacture of chloromethylated polystyrene [B]) 3 g of commercial grade monodisperse polystyrene (weight average molecular weight 107,000) and 50 ml of chloromethyl ether were charged into the same apparatus as in Reference Example 1, and the mixture was heated until a homogeneous solution was obtained. Stir at 30°C. Then anhydrous zinc chloride 0.5
g was added thereto, and the mixture was reacted at 35°C for 4 hours. Next, methanol:dioxane (1:1) solution 20
ml was added to stop the reaction, and the resulting reaction solution was poured into 300 ml of methanol:water (7:3) solution to precipitate the product, which was purified by reprecipitation in the same manner as in Reference Example 1 to obtain chloromethylated polystyrene. 3.2g was obtained.
Elemental analysis revealed that the chlorine content was 18.6%, and that 0.73 chloromethyl groups were introduced per benzene ring. Reference Example 3 (Production of chloromethylstyrene copolymer [C]) In a 4-necked 500ml flask equipped with a stirring bar, condenser, dropping funnel, and thermometer, 125g of distilled water,
4 g of Emulgen 935 emulsifier (polyoxyethylene nonylphenol ether surfactant manufactured by Kao Atlas Co., Ltd.) and 2 g of dodecyl mercaptan as a chain transfer agent were charged, and then styrene was added under stirring.
23.4g (0.225mol), 20g methyl methacrylate
(0.20 mol) and chloromethylstyrene (m-form
A mixture of 11.4 g (0.075 mol) of 60/P-isomer 40 was added. The temperature was raised to about 75°C, and 7.5 ml of a 2% aqueous solution of ammonium persulfate (0.3 wt% to monomer) was added dropwise over 1 hour, and the reaction was allowed to proceed for an additional 2 hours. The obtained reaction solution was salted out to precipitate the product. The produced white solid was washed with water and methanol, and then purified by reprecipitation using a methylene chloride-methanol system to obtain 48 g of chloromethylstyrene copolymer. According to NMR analysis, the composition ratio of this copolymer was styrene:methyl methacrylate:chloromethylstyrene=0.47:0.40:0.13 (molar ratio). Furthermore, the weight average molecular weight in terms of polystyrene was found to be approximately 100,000 by HLC analysis. Reference Example 4 (Production of chloromethylstyrene copolymer [D]) 31.2 g of styrene was placed in a 4-necked 500 ml flask equipped with a thermometer, condenser, nitrogen inlet, and stirring bar.
(0.03 mol), acrylonitrile 1.59 g (0.03 mol), chloromethylstyrene (m-form 60/P-form
40 mixture) 4.59g (0.03mol) and toluene 50ml
was charged, 0.14 g of azobisisobutyronitrile (1 mol % to monomer) was added as a catalyst, and the reaction was carried out at 70° C. for 6 hours in a nitrogen stream. The obtained reaction solution was concentrated by removing the solvent, and then poured into methanol to precipitate the product. Next, reprecipitation purification was performed using a methylene chloride-methanol system to obtain about 5.0 g of a pale yellow solid. From elemental analysis, the composition ratio of this copolymer is styrene:acrylonitrile:chloromethylstyrene=
The molar ratio was 0.33:0.28:0.39. Also,
According to HLC analysis, the weight average molecular weight in terms of polystyrene was approximately 8,800. Reference example 5 (Production of chloromethylstyrene copolymer [E]) 4.25g of methyl methacrylate in a glass sealed tube
(0.0425 mol), chloromethylstyrene (m-form
60/P-form 40 mixture) 1.14 g (0.0075 mol) and azobisisobutyronitrile 0.08 g as a catalyst
(1 mol % to monomer) was added and polymerized at 60° C. for 17 hours. The resulting reaction product was mixed with methylene chloride.
Precipitation purification using methanol system yields a white solid of approx. 4.4
I got g. According to elemental analysis, the composition ratio of this copolymer is methyl methacrylate: chloromethyl styrene = 0.84:
The molar ratio was 0.16. Furthermore, HLC analysis revealed that the weight average molecular weight in terms of polystyrene was approximately 105,000. Example 1 1-ethyl-4-hydroxymethyl-2,6,7-trioxabicyclo[2,2,2] was added to a four-necked 100 ml flask equipped with a stirring bar, condenser, dropping funnel, and nitrogen blowing tube. Octane 0.98g
(5.6 mmol) and 10 ml of dry tetrahydrofuran
After charging and dissolving, 0.25 g (5.1 mmol) of sodium hydride (50% oil suspension) was added at room temperature, and the mixture was reacted at 30° C. for 2 hours in a nitrogen stream. A solution of 1.94 g of chloromethylated polystyrene [A] dissolved in 15 ml of dry N,N-dimethylformamide was added dropwise to the resulting reaction solution, and the mixture was heated at 35°C.
The reaction mixture was allowed to react for 3 hours, and then allowed to stand overnight. Next, centrifugation is performed to remove the sodium chloride produced.
The supernatant was washed several times with n-hexane. Furthermore, precipitation purification with tetrahydrofuran-n-hexane was repeated to obtain 2.0 g of a white solid. The specific gravity of this product was 1.114 at 30°C. The composition ratio of this product was determined by NMR analysis as δ=
6.2~7.3ppm (φ-H), δ=4.3ppm (φ-CH ₂
-O), δ=3.95ppm (C-O-CH ₂ -C), δ=
It was determined from the peak integral value of 3.1 ppm (O-CH ₂ -C) (see Figure 1). The structure of this product is represented by the following formula. (Here, y/x+y=18/100.) Furthermore, the weight average molecular weight in terms of polystyrene determined by HLC analysis was about 290,000. Also, by IR analysis (KBr tablet method), 1095 cm ^-1 , 940 cm ^-1
Absorption of (C-O-CH ₂ ) was observed (see Figure 2). In addition, the specific gravity of the produced polymer in the examples was measured by the following method. Measurement method: Using a density gradient tube method B type direct reading specific gravity measuring device (Shibayama Kagaku Kikai Seisakusho), the sample was molded into a density gradient tube made from an aqueous potassium carbonate solution using a tablet molding machine for infrared absorption spectroscopy. , degassed in an aqueous potassium carbonate solution and poured into the sample. Example 2 The apparatus described in Example 1 was charged with 0.44 g (2.5 mmol) of 1-ethyl-4-hydroxymethyl-2,6,7-trioxabicyclo[2,2,2]octane and 10 ml of dry tetrahydrofuran. After the mixture was dissolved, 0.12 g (2.5 mmol) of sodium hydride (50% oil suspension) was added, and the mixture was reacted for 1.2 hours at 30° C. in a nitrogen stream. A solution of 0.50 g of chloromethylated polystyrene [B] dissolved in 30 ml of dry N,N-dimethylformamide was added dropwise to the resulting reaction solution, and the mixture was heated at 45°C for 2.5 g.
Allowed time to react. The reaction solution was concentrated by removing the solvent using a rotary evaporator, and then diluted with methanol 200 ml.
ml to precipitate the product. this product
Precipitation purification by dissolving in 10 ml of methylene chloride and precipitation from methanol was repeated twice to yield 0.56 g of a white solid. The specific gravity of this product was 1.162 at 30°C. The composition ratio of this product is expressed by the following formula based on NMR analysis and elemental analysis. Here {x/x+x'+y=27/100, x'/x+x'
+y=12/100 y/x+x'+y=61/100. } Furthermore, the weight average molecular weight in terms of polystyrene determined by HLC analysis was approximately 310,000. In addition, IR analysis showed 1100cm ^-1 , 940cm ^-1 (C-O
-CH ₂ ) absorption was observed (see Figure 3). Example 3 The apparatus described in Example 1 was equipped with 0.42 g (2.6 mmol) of 1-methyl-4-hydroxymethyl-2,6,7-trioxabicyclo[2,2,2]octane and 20 ml of dry tetrahydrofuran. After the mixture was dissolved, 0.12 g (2.6 mmol) of sodium hydride (50% oil suspension) was added and the mixture was reacted at 30° C. for 1 hour in a nitrogen stream. Add 20 ml of dry N,N-dimethylformamide to the resulting reaction solution.
A solution containing 1.0 g of chloromethylated polystyrene [A] was added dropwise to the solution, reacted at 30°C for 3 hours, and then left overnight. Next, centrifugation was performed to remove the generated salts, and precipitation purification was performed in the same manner as in Example 1 to obtain 0.71 g of a white solid. The specific gravity of this product was 1.109 at 25°C. The composition ratio of this product was determined by NMR analysis as δ
=6.2~7.3ppm(φ-H), δ=4.3ppm(φ-
CH2 _- O), δ=4.0ppm(C- _CH2 -O-C),
It was determined from the peak area value of δ = 3.1 ppm (O-CH ₂ -C). The structure of this product is represented by the following formula. Here (x/x+x'+y=82/100, x'/x+x'
+y=3/100 y/x+x'+y=15/100. ) Also, the weight average molecular weight in terms of polystyrene determined by HLC analysis was approximately 360,000. The IR chart of the product is shown in Figure 4. Example 4 The apparatus described in Example 1 was equipped with 0.80 g (4.6 mmol) of 1-ethyl-4-hydroxymethyl-2,6,7-trioxabicyclo[2,2,2]octane and 10 ml of dry tetrahydrofuran. After dissolving, add 0.20 g (4.2 mmol) of sodium hydride (50% oil suspension) and
The reaction was carried out at ℃ for 1 hour. A solution of 1.5 g of chloromethylstyrene copolymer [C] dissolved in 15 ml of dry N,N-dimethylformamide was added dropwise to the resulting reaction solution, and the mixture was allowed to react at 30° C. for 4 hours and then left overnight. Next, centrifugation was performed to remove the generated salts, and precipitation purification was performed in the same manner as in Example 1 to obtain 1.6 g of a white solid. The specific gravity of this product was 1.149 at 30°C. The composition of the product was determined by NMR analysis to be δ=6.2-7.3ppm (φ-H), δ=
4.3ppm (φ-CH ₂ -O), δ = 4.0ppm (C-CH ₂
-O-C), was determined from the peak area value of δ = 2.5 to 3.6 ppm. The structure of this product is represented by the following formula. Here (x/x+x'+y=47/100,x'/x+x'
+y=39/100 y/x+x'+y=13/100. ) Also, the weight average molecular weight in terms of polystyrene determined by HLC analysis was approximately 220,000. Also, by IR analysis, 1730cm ^-1 (ester), 1100cm ^-1 , 945cm
^-1 (C-O-CH ₂ ) absorption is observed (see Figure 5). Example 5 The apparatus described in Example 1 was equipped with 0.35 g (2.0 mmol) of 1-ethyl-4-hydroxymethyl-2,6,7-trioxabicyclo[2,2,2]octane and 5 ml of dry tetrahydrofuran. After dissolving, add 0.09 g (1.8 mmol) of sodium hydride (50% oil suspension) and
The reaction was carried out at ℃ for 1 hour. A solution of 0.5 g of chloromethylstyrene copolymer [D] dissolved in 10 ml of dry N,N-dimethylformamide was added dropwise to the resulting reaction solution, and the mixture was allowed to react at 30° C. for 3 hours and then left overnight. Next, centrifugation was performed to remove the generated salts, and the supernatant was partially solvent-removed using a rotary evaporator, and then poured into methanol for precipitation. The product was purified by reprecipitation in a tetrahydrofuran-n-hexane system, resulting in a pale yellow solid of 0.57 g.
I got g. The specific gravity of this product was 1.161 at 25°C. According to NMR analysis, the composition ratio of this product is δ = 6.2
~7.3ppm (φ-H), δ=4.3ppm (φ-CH ₂ −
O), δ = 4.0 ppm (C-O-CH ₂ -C). The structure of this product is represented by the following formula. Here (x/x+x'+x"y=33/100, x'/x+x'+x"+y=28/100, x"/x+x'+x"+y=12/100, y/x+x'+x"+y=27 /100) Furthermore, the weight average molecular weight in terms of polystyrene determined by HLC analysis was approximately 9000. Also, by IR analysis, 2240 cm ^-1 (nitrile), 1100 cm ^-1 , 950 cm ^-1 (C
-O-CH ₂ ) absorption is observed (see Figure 6). Example 6 The apparatus described in Example 1 was charged with 0.78 g (4.5 mmol) of 1-ethyl-4-hydroxymethyl-2,6,7-trioxabicyclo[2,2,2]octane and 10 ml of dry tetrahydrofuran. After charging and dissolving, 0.22 g (4.5 mmol) of sodium hydride (50% oil suspension) was added and reacted at 30° C. for 1 hour. A solution of 1 g of chloromethylstyrene copolymer [E] dissolved in 20 ml of dry N,N-dimethylformamide was added dropwise to the resulting reaction solution, and the mixture was allowed to react at 30° C. for 4 hours and then left overnight. Next, centrifugation was performed to remove the generated salts, and the supernatant was precipitated with n-hexane. The product was purified by reprecipitation using a tetrahydrofuran-n-hexane system to obtain 0.85 g of a white solid. The specific gravity of this product was 1.168 at 25°C, and the composition of the product was determined by NMR analysis. The structure of this product is represented by the following formula. (Here, y/x+y=16/100.) Furthermore, the weight average molecular weight in terms of polystyrene determined by HLC analysis was about 130,000. The IR chart of the product is shown in FIG. Reference Examples 6 to 11 (Crosslinking of polymers) The polymer products obtained in Examples 1 to 6 were dissolved in about 20 times the amount of 1,1-dichloroethane, and BF ₃ O ( C ₂ H ₅ ) ₂ was added at a ratio of about 1 wt% to the polymer and reacted at 60° C. for 24 hours to obtain a crosslinked polymer. The specific gravity of this crosslinked polymer was measured at the same temperature at which the polymer before crosslinking was measured, and the volume change due to crosslinking was calculated using the following formula. Volumetric expansion rate (%) = (specific gravity of polymer before crosslinking/specific gravity of crosslinked polymer - 1
)×100

【table】

[Table] From the above results, it is recognized that the styrenic polymer of the present invention substantially does not shrink or, on the contrary, expands during crosslinking.

[Brief explanation of the drawing]

Figure 1 is an NMR spectrum diagram of the product obtained in Example 1, Figure 2 is an IR spectrum diagram of the product obtained in Example 1, and Figure 3 is an IR spectrum diagram of the product obtained in Example 2. IR spectrum diagram, Figure 4 is Example 3
Figure 5 is an IR spectrum diagram of the product obtained in Example 4.
Figure 6 is an IR spectrum diagram of the product obtained in Example 5, and Figure 7 is an IR spectrum diagram of the product obtained in Example 6.
An IR spectrum diagram is shown.

Claims (1)

[Claims] Primary formula: (wherein A represents a monomer unit composed of at least one ethylenically unsaturated compound, and R
represents a lower alkyl group, and x and y represent the mole fraction of each structural unit. ), and the ratio of x and y is y/(x+y)=1/100
A styrenic polymer into which a bicycloorthoester group is introduced, which has a weight average molecular weight of 1,000 to 600,000 in terms of polystyrene.