JPH0128055B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to modified copolymers of ethylenically unsaturated compounds. 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 approximately 1 to 2.5% (Kobunshi, Vol. 27, February issue, 1978, No. 108-111)
(see page). 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 extensive research in order to develop such a non-shrinkable polymer, the present inventors decided to radically copolymerize a specific 1-vinyl-bicycloorthoester compound with a conventionally known ethylenically unsaturated compound. Therefore, it has been found that when a bicycloorthoester group is introduced into the ethylenically unsaturated compound, the resulting copolymer does not shrink during crosslinking due to ring opening of the orthoester group, but on the contrary expands by about 1%. As a result, the present invention was completed. Thus, the present invention provides the following formula: (In the formula, A represents a monomer unit composed of at least one ethylenically unsaturated compound, except when monomer unit A is composed of styrene alone, and R is a lower alkyl x and y represent the mole fraction of each monomer unit, and the y/(x+y) ratio is in the range of 3/100 to 50/100), and has a weight average molecular weight Provided is a modified copolymer of an ethylenically unsaturated compound having a bicycloorthoester group, having a molecular weight in the range of 1,000 to 10,000,000. A copolymer consisting of structural units of the formula () according to the present invention includes one or more ethylenically unsaturated monomers and the following formula (): 1-vinyl-4-alkyl-2,6,7-trioxabicyclo[2,2,2]octane (wherein R represents a lower alkyl group such as methyl, ethyl, probyl or butyl) It can be produced by radical copolymerization with at least one compound. The present inventors previously discovered that the compound of formula () undergoes not only radical polymerization but also cationic ring-opening polymerization, and filed a patent application for the compound of formula () (Japanese Patent Application No. 11433/1989). reference). As described in the same specification, the compound of formula () is represented by the following formula (): 1-methyl halide-4
-Alkyl-2,6,7-trioxabicyclo[2,2,2]octane can be produced by dehydrohalogenation reaction. (Here, X is a halogen atom such as Cl, Br, I, etc.). The above reaction is carried out in a suitable solvent, for example tetrahydrofuran, with an alkali, for example t-
This is carried out by dehydrohalogenation by the action of butoxypotassium. The degree of progress of the reaction is
This can be easily determined by analyzing the reaction solution using, for example, liquid chromatography. Compound () can be isolated from the reaction solution by, for example, pouring the reaction solution into water and using an organic solvent such as ether or benzene. This can be carried out by extracting, dehydrating and drying the organic layer, distilling off the solvent, and distilling the residue under reduced pressure. Ethylenically unsaturated compounds that can induce monomer unit A in formula () by radical copolymerization with bicycloorthoester compounds () include known compounds that can radically copolymerize with vinyl monomers. Almost any can be used, specific examples of which include the compounds listed below. Esters of acrylic acid and methacrylic acid, such as methyl, ethyl, propyl, butyl esters of acrylic acid and methacrylic acid (acrylic acid,
Free carboxylic acids such as methacrylic acid are not preferred because they tend to open the bicycloorthoester ring of compound () during radical copolymerization; styrene and substituted styrenes, such as divinylbenzene, o
-, m- or p-chlorostyrene, m- or p-
Chlormethylstyrene, α-methylstyrene, p
-methoxystyrene, p-dimethylaminostyrene, p-cyanostyrene, p-nitrostyrene,
α-acetoxystyrene, etc. (However, styrene cannot be used alone because it does not copolymerize with compound (), but it can be used in combination with other monomers); 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, cinnamate nitrile; vinyl benzoate, allyl benzoate; and unsaturated carboxylic acid anhydrides, e.g. Maleic anhydride, itaconic anhydride, citraconic anhydride, etc. Preferred ethylenically unsaturated compounds that may be used are of the following formula: (In the formula, R ₁ is hydrogen or an alkyl group, and R ₂ is -CN, -COOR ₃ , -OCOR ₃ , phenyl, or a phenyl group having alkyl, halogen, or haloalkyl as a substituent, provided that R ₁ except when is hydrogen and R ₂ is phenyl,
R ₃ is an alkyl group) and anhydrides of maleic acid, itaconic acid and citraconic acid. Radical copolymerization of the compound of formula () and an ethylenically unsaturated compound can be carried out by ordinary radical polymerization means,
For example, it can be carried out using ultraviolet rays, infrared rays, heat, electron beams or microwaves. In ultraviolet radical polymerization, a photoinitiator is usually used. Suitable photoinitiators include acetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxyacetophenone, 4'-isopropyl-2-hydroxy-2
-Methylpropiophenone, 2-hydroxy-2
-methylpropiophenone, 4,4'-bis(diethylamino)benzophenone, benzophenone,
Methyl-(0-benzoyl)-benzoate, 1-
Phenyl-1,2-propanedione-2-(0-
ethoxycarbonyl)-oxime, 1-phenyl-1,2-propanedione-2-(0-benzoyl)-oxime, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin butyl ether, benzoin octyl ether, benzyl or Carbonyl compounds such as diacetyl; methylanthraquinone, chloroanthraquinone, chlorothioxanthone, 2-methylthioxanthone or 2-
anthraquinone or xanthone derivatives such as i-propylthioxanthone; diphenyl sulfide;
Sulfur compounds such as diphenyl disulfide or dithiocarbamate; α-chloromethylnaphthalene,
There are anthracene etc. In the polymerization using infrared rays, heat, or microwaves, any radical initiator can be used as long as it can generate radicals by decomposition. For example, di-tert-butyl peroxide,
2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, tert-butyl hydroperoxy
Organic peroxides such as oxide, tert-butylperoxybenzoate; azo compounds such as 2,2'-azobisisobutyronitrile; ammonium persulfate,
Persalts such as potassium persulfate can be used. Further, polymerization using ionizing radiation such as an electron beam is usually carried out without a catalyst. When a catalyst is used, the amount used is generally 0.01 to 10 wt%, preferably 0.1% based on the total amount of monomers.
~5wt% range. Radical polymerization proceeds even at room temperature when irradiated with ultraviolet rays or ionizing radiation, but in other cases it proceeds smoothly under heating or heating conditions. As the polymerization method, any of bulk, solution, suspension and emulsion polymerization can be employed, but bulk or solution polymerization is usually convenient. When using a solvent, for example, ethers such as dioxane, alicyclic hydrocarbons such as cyclohexane, aromatic hydrocarbons such as toluene and xylene, halogenated alkanes such as dichloroethylene, ketones such as methyl ethyl ketone, methyl isobutyl ketone, etc. Cellosolves such as methyl cellosolve and ethyl cellosolve are commonly used. The produced copolymer is prepared by dissolving it in a solvent in which the produced polymer is soluble, such as methylene chloride, dioxane, dimethylformamide, etc.
For example, the copolymer can be separated and purified by repeating several times the operation of adding the copolymer dropwise to a precipitation solvent such as n-hexane or methanol under stirring to precipitate the copolymer. In the modified copolymer of the present invention, if the monomer unit derived from the bicycloorthoester compound of formula () is present in the copolymer at about 1 mol%, the volume shrinkage during crosslinking is substantially improved. Because it can be done,
Molar ratio y/x of monomer units in the above formula ()
+y may be present in any proportion within 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, so the y/x+y ratio needs to be in the range of 3/100 to 50/100. be. Further, the copolymer according to the present invention has a molecular weight similar to that of a normal copolymer obtained by polymerizing ethylenically unsaturated compounds by radical polymerization, and specifically, 1,000 to 1,000. It has a weight average molecular weight of 10,000. Since the copolymer of the present invention has a volume-expandable bicycloorthoester group in its molecule, it exhibits the property of substantially expanding its volume upon cross-linking and curing, and also exhibits properties such as heat resistance and solvent resistance due to cross-linking. The physical properties of the material are improved. Thus, the copolymer of the present invention eliminates the above-mentioned drawbacks associated with volumetric shrinkage, and can be used for paints with good adhesion that do not cause voids, adhesives that do not cause internal distortion, and composite materials and adhesives that require dimensional accuracy. Extremely useful for manufacturing mold materials, etc. For example, the copolymer of the present invention is dissolved in a suitable solvent and applied to the substrate surface,
The formed coating film can be cured by suitable crosslinking means to obtain an excellent coating film, and it can also be crosslinked after injection into a mold to obtain an improved molded article. The copolymer 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 ,
Lewis acids such as FeCl ₃ , SnCl ₃ , SbCl ₅ , SbF ₃ , TiCl ₄ ; Coordination compounds of Lewis acids such as BF ₃ OEt ₂ , BF ₃ -aniline complexes, etc. and compounds containing O, S, N, etc. ; Examples include oxonium salts, diazonium salts, carbonium salts, halogen compounds, mixed halogen compounds, and perhalogen acid derivatives of Lewis acids. The amount of catalyst used is generally in the range of 0.001 to 10% by weight based on the copolymer to be crosslinked. There are no particular restrictions on polymerization temperature, but it is usually room temperature to 200℃.
It will be held in Further, crosslinking can also be carried out by irradiation with radiation such as electron beams and ultraviolet rays. In the case of ultraviolet irradiation, for example, φ-N ⁺
Aromatic diazonium salts such as ≡N・PF ₆ ⁻ , φ−N ⁺ ≡N・BF ₄ ⁻ ; aromatic halonium salts such as φ−I ⁺ −φ・BF ₄ ⁻ ;

Aromatic onium salts of Group A elements of the periodic table such as [Formula];

Aromatic onium salts of elements of group a of the periodic table, such as: ##STR1## may be used. When the above-mentioned acid anhydride is used as the ethylenically unsaturated monomer, the resulting copolymer can be crosslinked simply by the presence of a small amount of water. Next, the present invention will be further explained by reference examples and examples. Reference Example 1 (Production of compound of formula ()) Using a 250 ml flask, add 11 g (0.1 mol) of potassium t-butoxy to 100 ml of tetrahydrofuran.
1-bromoethyl-4-ethyl-2,6,7-trioxabicyclo[2,2,
2] 25 g (0.1 mol) of octane was added dropwise at room temperature over about 1 hour. After further reacting at reflux temperature for 5 hours, the reaction solution was poured. The solution was extracted with ether, the organic layer was dried over magnesium sulfate, and the ether was evaporated. By further distilling the evaporation residue under reduced pressure, 1-
14 g of vinyl-4-ethyl-2,6,7-trioxabicyclo[2,2,2]octane was obtained. The yield was 83%, and the physical properties are as follows. Γ elemental analysis (%); Actual value --- C; 63.4, H; 8.3 Calculated value as C ₉ H ₁₄ O ₃ (theoretical value) --- C;
63.5, H 8.2 Γ Boiling point; 68-72℃/2 mmHg Γ Infrared absorption spectrum; 1100 cm ^-1 (ether), 990 cm ^-1 (CH ₂ = CH-) Γ Nuclear magnetic resonance spectrum (in CDCl ₃ ); δ (ppm ); 0.6−1.4 (5H, Et), 4.0 (6H, −CH ₂
-O-), 5.2-6.0 (3H, _CH2 =CH-). In the following examples, the specific gravity of the produced copolymer was measured by the following method. Measurement method A: Density gradient tube method Using a type B direct reading specific gravity measuring device (Shibayama Kagaku Kikai Seisakusho), a sample was molded into a density gradient tube made of an aqueous potassium carbonate solution using a tablet molding machine for infrared absorption spectroscopy. After that, it was degassed in an aqueous potassium carbonate solution and then poured into the sample for measurement. Measurement method B: Heat the sample above its melting point, melt and degas it, then put it into the density gradient tube and measure. The average molecular weight of the produced polymer was calculated as a polystyrene equivalent molecular weight from liquid chromatography analysis. The measurement conditions are as follows. Apparatus: HLC-801A manufactured by Toyo Soda Kogyo Co., Ltd. Column: TSK gel-GMH6 2 bottles Eluent: Tetrahydrofuran flow rate: 1 ml/min Example 1 In a sealed glass tube, 1.72 g (0.02 mol) of vinyl acetate, 1-vinyl-4-ethyl-2,6,7-trioxabicyclo[2,2,2]octane 3.4g
(0.02 mol) and 0.20 g of 2,2'-azobisisobutyronitrile (3 mol% based on the total amount of monomers) as a catalyst were charged, and the tube was sealed and polymerized at 70°C for 24 hours. . The obtained product was dissolved in about 20 ml of methylene chloride, and this solution was added dropwise to about 250 ml of n-hexane with stirring to precipitate the polymer. This precipitate was filtered and dissolved again in about 20 ml of methylene chloride.
Similarly, it was dropped into about 250 ml of n-hexane for precipitation. Furthermore, the precipitation purification was repeated again to obtain 2.5 g of a white powdery copolymer. The specific gravity of this copolymer was 1.220 (measurement method A) at 25°C.
The composition ratio of this copolymer was determined by nuclear magnetic resonance spectrum (NMR) analysis (in deuterated chloroform) as δ=
3.92ppm ( _CH2 -O,s) and δ=2.04ppm

It was determined from the peak integral value of [Formula]. In addition, infrared absorption spectrum (IR) (KBr tablet method) analysis shows approximately 950 cm ^-1 (C-O-CH ₂ ), approximately 1240 cm ^-1 and 1740 cm -1 (C-O-CH 2 ).
Characteristic absorption of cm ^-1 (ester) was observed (first
(see figure). Further, this polymer had a polystyrene equivalent weight average molecular weight of about 7000 as determined by liquid chromatography (HLC) analysis. The structure of this polymer is shown by the following formula. (Here y/x+y=35/100) Example 2 Vinyl acetate 4.3g (0.05 mol), 1-vinyl-4
-ethyl-2,6,7-trioxabicyclo[2,2,2]octane 1.7 g (0.01 mol) and 2,2'-azobisisobutyronitrile as catalyst
0.30 g (3 mol % vs. charge ratio) was polymerized in the same manner as in Example 1, and purified by precipitation using a methylene chloride-n-hexane system to obtain 3.8 g of a white powdery copolymer.
The specific gravity of this copolymer was 1.206 (measurement method B) at 25°C. The composition ratio of this copolymer was determined by NMR analysis to be δ=3.88ppm (CH ₂ −O, s) and δ
=2.02ppm

It was determined from the peak integral value of [Formula]. In addition, IR analysis revealed that approximately 950 cm ^-1 (C-O-
Characteristic absorptions of CH ₂ ), approximately 1240 cm ^-1 and 1740 cm ^-1 (ester) were observed (see Figure 2). Furthermore, the weight average molecular weight in terms of polystyrene determined by liquid chromatography (HLC) analysis was approximately 19,000. The structure of this copolymer is represented by the following formula. (Here y/x+y=19/100) Example 3 Vinyl acetate 4.3g (0.05 mol), 1-vinyl-4
-ethyl-2,6,7-trioxabicyclo[2,2,2]octane 0.85 g (0.005 mol) and 2,2'-azobisisobutyronitrile as catalyst
0.27 g (3 mol % based on the total amount of monomers) was polymerized and purified in the same manner as in Example 1 to obtain 3.9 g of a white powdery copolymer. The specific gravity of this polymer was 1.205 (measurement method B) at 25°C. The composition ratio of this copolymer was determined by NMR analysis in the same manner as in Example 1. Also, according to IR analysis, approximately 950 cm ^-1 (C-O-CH ₂ ),
Characteristic absorptions were observed at approximately 1240 cm ^-1 and 1740 cm ^-1 (ester) (see Figure 3). In addition, the weight average molecular weight in terms of polystyrene determined by HLC analysis is approximately 69,000.
It was hot. The structure of this copolymer is represented by the following formula. (Here, y/x+y=10/100) Example 4 1.33 g of acrylonitrile in a glass sealed tube
(0.025 mol), 1-vinyl-4-ethyl-2,6,
7-trioxabicyclo[2,2,2]octane
4.25 g (0.025 mol) and 0.22 g (3 mol % based on the total amount of monomers) of di-t-butyl peroxide as a catalyst were charged, and after the tube was sealed, polymerization was carried out at 70° C. for 24 hours. The obtained polymer was diluted with methylene chloride.
The copolymer was purified by precipitation using n-hexane to obtain 2.5 g of a white powdery copolymer. The specific gravity of this copolymer was 1.281 (measurement method A) at 25°C. In addition, the composition ratio of this copolymer is determined by elemental analysis of the nitrogen content (9.94%).
I asked for it from In addition, IR analysis revealed that approximately 950cm ^-1 (C-
O-CH ₂ ), a characteristic absorption was observed at about 2230 cm ^-1 (nitrile) (see Figure 4). Furthermore, the weight average molecular weight in terms of polystyrene determined by HLC analysis was approximately 9,400. The structure of this copolymer is represented by the following formula. (Here, y/x+y=34/100) Example 5 After polymerization in the same manner as in Example 1, using 2.0 g (0.02 mol) of methyl methacrylate instead of vinyl acetate, methylene chloride- White powdery copolymer 1.6 is obtained by precipitation and purification with n-hexane system.
I got g. The specific gravity of this copolymer at 25℃ is
It was 1.192 (Measurement method B). The composition ratio of this copolymer was determined by NMR analysis to be δ = 4.32 ppm (CH ₂ -O,
s) and δ=3.63ppm

It was determined from the peak integral value of [Formula]. Also, according to IR analysis, approximately 960
Characteristic absorptions were observed at cm ^-1 (C-O-CH ₂ ), about 1145 cm ^-1 and 1730 cm ^-1 (ester) (see Figure 5).
Furthermore, the weight average molecular weight in terms of polystyrene determined by HLC analysis was approximately 20,000. The structure of this copolymer is represented by the following formula. (Here, y/x+y=5/100) Example 6 2.0 g (0.02 mol) of methyl methacrylate, chloromethylstyrene (60 m-isomer/40 p-isomer mixture)
3.06g (0.02mol), 1-vinyl-4-ethyl-
2,6,7-trioxabicyclo[2,2,2]
3.4 g (0.02 mol) of octane and 0.3 g (3 mol% based on the total amount of monomers) of 2,2'-azobisisobutyronitrile were charged into a glass sealed tube, and polymerization was carried out in the same manner as in Example 1. I let it happen. The obtained polymer was purified by precipitation in the same manner as in Example 1 to obtain 4.75 g of a white powdery copolymer. The specific gravity of this copolymer was 1.216 (measurement method A) at 25°C. The composition ratio of this copolymer is NMR
From the analysis, δ=4.5ppm (CH ₂ −Cl), δ=3.8ppm (O
-CH ₂ ) and other peak integral values. The structure of this copolymer is represented by the following formula. (Here, x/x+x′+y=40/100, x′/x+x′+y
= 57/100, y/x+x'+y=3/100. ) In addition, IR analysis revealed that approximately 710 cm ^-1 (phenyl), approx.
Characteristic absorptions were observed at 1140 cm ^-1 , 1190 cm ^-1 and 1730 cm ^-1 (ester) (see Figure 6). Furthermore, the weight average molecular weight in terms of polystyrene determined by HLC analysis was approximately 60,000. Reference Examples 1 to 6 (Crosslinking of copolymers) The copolymers obtained in Examples 1 to 6 were dissolved in about 20 times the amount of methylene chloride, and BF ₃ O (C ₂ H ₅ ) ₂ was added at a ratio of about 0.03 mol to 1 equivalent of bicycloorthoester group in the copolymer, and the mixture was reacted at room temperature for 24 hours to obtain a crosslinked polymer. The specific gravity of this crosslinked polymer was measured at 25°C, and the volume change due to crosslinking was calculated.

[Table] 〓 Body specific gravity 〓
Example 7 Chloromethylstyrene (m-isomer 60/p-isomer 40 mixture) 3.06 g (0.02 mol), 1-vinyl-4-ethyl-2,6,7-trioxabicyclo[2,
2,2] octane 3.4 g (0.02 mol) and 2,2'-
0.2 g of azobisisobutyronitrile (3 mol % based on the total amount of monomers) was charged into a glass sealed tube, and polymerization and precipitation purification were performed in the same manner as in Example 1 to obtain a white powdery copolymer 3.0 g. I got g. The specific gravity of this copolymer was 1.221 (measurement method A) at 25°C. The composition ratio of this copolymer was determined by NMR analysis to be δ=4.5ppm.
( _CH2 -Cl), δ=3.8ppm (O- _CH2 ). The structure of this copolymer is represented by the following formula. (Here, y/x+y=6/100.) Furthermore, the weight average molecular weight in terms of polystyrene determined by HLC analysis was about 35,000. Example 8 Maleic anhydride 1.96 g (0.02 mol), 1-vinyl-4-ethyl-2,6,7-trioxabicyclo[2,2,2]octane 3.4 g (0.02 mol),
0.2 g of 2,2'-azobisisobutyronitrile (3 mol % based on the total amount of monomers) and 20 ml of dioxane as a solvent were charged into a glass sealed tube, and polymerization was carried out in the same manner as in Example 1. Then, precipitation purification was carried out in the same manner as in Example 1 using a dioxane-n-hexane solvent in a dry box to obtain 5.6 g of a white powdery copolymer. From NMR analysis, the structure of this copolymer is shown by the following formula. (Here, y/x+y=41/100.) Also, according to IR analysis, approximately 1770 cm ^-1 and 1850 cm ^-1 (-CO
-O-CO-) characteristic absorption was observed (see Figure 7). Furthermore, the weight average molecular weight in terms of polystyrene determined by HLC analysis was approximately 7,900. Example 9 Styrene 2.08g (0.02mol), maleic anhydride
1.96g (0.02mol), 1-vinyl-4-ethyl-
2,6,7-trioxabicyclo[2,2,2]
3.4 g (0.02 mol) of octane, 0.3 g (3 mol % based on the total amount of monomers) of 2,2'-azobisisobutyronitrile, and 20 ml of dioxane as a solvent were charged into a glass sealed tube, Polymerization and purification were carried out in the same manner as in Example 6 to obtain 5.3 g of a white solid copolymer. The composition ratio of this copolymer was determined from elemental analysis values. The structure of this copolymer is represented by the following formula. (Here, x/x+x′+y=37/100, x′/x+x′+y
= 37/100, y/x+x'+y=25/100. ) Also, from IR analysis, 950cm ^-1 (O-CH ₂ ), approximately 1775cm
^-1 and 1855 cm ^-1 (-CO-O-CO-) (see Figure 8). Furthermore, the weight average molecular weight in terms of polystyrene determined by HLC analysis was approximately 55,000. Reference Example 7 0.2 g of the copolymer obtained in Example 7 was dissolved in 20 ml of methylene chloride, and about 0.003 g of BF ₃ O(C ₂ H ₅ ) ₂ was dissolved.
In addition, a crosslinked polymer was obtained by reacting at room temperature for 24 hours. Reference Example 8 0.2 g of the copolymer obtained in Example 8 was dissolved in 20 ml of methylene chloride, and about 0.003 ml of BF ₃ .O(C ₂ H ₅ ) ₂ was added at room temperature. A white precipitate formed immediately and a crosslinked copolymer was obtained. Reference Example 9 0.2 g of the copolymer obtained in Example 9 was dissolved in 20 ml of methylene chloride, and about 0.003 g of BF ₃ .O(C ₂ H ₅ ) ₂ was dissolved.
was added and allowed to react at room temperature for 24 hours. A white precipitate formed and a crosslinked copolymer was obtained. Reference Example 10 A 10% dioxane solution of the copolymer obtained in Example 9 was applied onto an aluminum plate and left at room temperature for 5 days, resulting in the formation of a crosslinked coating.

[Brief explanation of drawings]

Figures 1 to 8 are charts of infrared absorption spectra (KBr tablets) of copolymers according to the present invention obtained in Examples, respectively.

Claims (1)

[Claims] Primary formula: (In the formula, A represents a monomer unit composed of at least one ethylenically unsaturated compound, except when monomer unit A is composed of styrene alone, and R is a lower alkyl x and y represent the mole fraction of each monomer unit, and the y/(x+y) ratio is in the range of 3/100 to 50/100), and has a weight average molecular weight A modified copolymer of an ethylenically unsaturated compound having a bicycloorthoester group, the number of which is in the range of 1,000 to 10,000,000. 2 A is the following formula: (In the formula, R ₁ is hydrogen or an alkyl group, and R ₂ is -CN, -COOR ₃ , -OCOR ₃ , phenyl, or a phenyl group having an alkyl, halogen, or haloalkyl as a substituent, provided that R ₁ is A patent that is a monomer unit composed of one or more ethylenically unsaturated compounds represented by hydrogen, R ₂ is a phenyl group, and R ₃ is an alkyl group) A copolymer according to claim 1. 3. The copolymer according to claim 1, wherein A is a monomer unit composed of maleic anhydride, itaconic anhydride, or citraconic anhydride. 4 Claims 1 to 3 in which R is an ethyl group
The copolymer according to any of the above.