JPH07149837A - Alkali-soluble polymer - Google Patents

Abstract

PURPOSE:To convert an alkali-soluble copolymer into a flexible copolymer excellent in strength without causing either blocking or whitening. CONSTITUTION:This alkali-soluble copolymer is obtained by copolymerizing a monomer component of 10-25wt.% at least one of acrylic acid and methacrylic acid with 50-89wt.% at least one of an acrylic acid ester having a l-5C alkyl group and a methacrylic acid ester having a 1-5C alkyl group, 1-10wt.% acrylonitrile and 0-30wt.% other unsaturated monomers copolymerizable with the monomers and has 80-200mg KOH/g acid value, 10000-300000 number-average molecular weight and 15-40 deg.C glass transition temperature. Ethyl acrylate is used as the acrylic acid ester having the 1-5C alkyl group and stearyl acrylate is used as the other unsaturated monomers in an amount of 1-15wt.%.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to alkali-soluble polymers.

[0002]

A polymer obtained by copolymerizing at least one of an acrylic acid ester and a methacrylic acid ester with an unsaturated carboxylic acid has a carboxyl group derived from an unsaturated carboxylic acid, and therefore is a basic liquid. It is soluble and has film-forming ability because it is copolymerized with acrylic acid ester or methacrylic acid ester, and is usually insoluble in neutral liquid.

Since an alkali-soluble polymer film is dissolved and removed by a basic liquid, it can be used for various purposes such as packaging and surface protection, and when it is unnecessary, it can be easily carried out without damaging the contents or the surface of the object to be protected. Can be removed. JP-A-60-15
In JP 5212, an alkali-soluble polymer capable of forming a film capable of shrinking in water was proposed. This alkali-soluble polymer is obtained by copolymerizing at least one of acrylic acid and methacrylic acid, and an ester of acrylic acid and an alcohol having 1 to 18 carbon atoms (particularly, methyl acrylate, ethyl acrylate). In addition to those monomers, vinyl ether having 3 to 18 carbon atoms (in particular, vinyl isobutyrate), aromatic vinyl hydrocarbon having 8 to 11 carbon atoms (in particular, Acrylic ester (especially acrylic acid n) with styrene) and alcohol having 1 to 18 carbon atoms
-Butyl) or methacrylic acid ester (especially butyl methacrylate, stearyl methacrylate) may be copolymerized.

[0004]

The alkali-soluble polymers described in the above publications have the drawbacks that they tend to cause blocking and are fragile, so that they cannot be used in close contact with each other or are inconvenient to handle. . Therefore, a lubricant was added to the alkali-soluble polymer to prevent blocking, and a plasticizer was added to eliminate brittleness and enhance flexibility.

However, when a lubricant is added to the alkali-soluble polymer, the surface of the molded product is remarkably whitened and the quality is impaired. Further, when a plasticizer is added to the alkali-soluble polymer, the surface becomes tacky, which causes blocking and also lowers the strength. An object of the present invention is to provide an alkali-soluble polymer that is flexible and has excellent strength without causing blocking or whitening.

[0006]

In order to solve the above problems, the present invention provides at least one of acrylic acid and methacrylic acid [hereinafter referred to as "(meth) acrylic acid"] 10 to 25% by weight. At least one of an acrylic acid ester having an alkyl group having 1 to 5 carbon atoms and a methacrylic acid ester having an alkyl group having 1 to 5 carbon atoms [hereinafter, referred to as "(meth) acrylic acid lower alkyl ester" 50 to 89% by weight, acrylonitrile 1 to 10% by weight, and other unsaturated monomers copolymerizable with these monomers (hereinafter referred to as "copolymerized monomers") 0 An alkali-soluble polymer having an acid value of 80 to 200 mgKOH / g, a number average molecular weight of 10,000 to 300,000, and a glass transition temperature of 15 to 40 ° C., which is obtained by polymerizing 30 to 30% by weight of a monomer component, is provided.

The polymer of the present invention comprises an acrylic acid ester having an alkyl group having 18 to 30 carbon atoms and a methacrylic acid ester having an alkyl group having 18 to 30 carbon atoms as the copolymerizable monomer. At least one of
One (hereinafter referred to as “(meth) acrylic acid long-chain alkyl ester”) 1 to 15% by weight may be copolymerized.

The polymer of this invention may also be a film. The alkali-soluble polymer of the present invention is 80
~ 200 mgKOH / g, preferably 110-180 mgKOH / g
Has an acid value of. If the acid value of the polymer is less than the above range, the polymer is not soluble in alkali, and if it exceeds the above range, the polymer becomes brittle. The polymer of this invention is 10,000 to 30
It has a number average molecular weight of 10,000, preferably 50,000 to 200,000. When the number average molecular weight of the polymer is less than the above range, the strength of the polymer is weak and the polymer cannot be used. When it exceeds the above range, moldability into a film is deteriorated.

The polymers of this invention have a glass transition temperature of 15-40 ° C, preferably 20-35 ° C. If the glass transition temperature of the polymer is below the above range, blocking occurs due to the phase transition of the polymer, and if it exceeds the above range, the polymer becomes hard and a flexible film cannot be formed. To make the polymer of this invention, (meth) acrylic acid is added in an amount of 10 to 25% by weight, preferably 14% by weight, based on the total weight of the monomers.
Used for polymerization in an amount of ~ 23% by weight. When (meth) acrylic acid is used in an amount smaller than the above range, the polymer cannot be provided with an acid value within the above range by (meth) acrylic acid. Further, when (meth) acrylic acid is used in an amount larger than the above range, the hydrophilicity of the polymer is excessively increased, so that the polymer may become sticky due to moisture absorption or may be soluble in pure water.

To make the polymer of this invention, (meth)
Acrylic acid lower alkyl ester is used for the polymerization in an amount of 50 to 89% by weight, preferably 60 to 80% by weight, based on the total weight of the monomers. If the lower alkyl (meth) acrylic acid ester is used in an amount less than the above range, it becomes difficult to form the polymer into a film. Further, when the (meth) acrylic acid lower alkyl ester is used in an amount larger than the above range, the amount of (meth) acrylic acid becomes small and the polymer becomes substantially insoluble in alkali. The (meth) acrylic acid lower alkyl ester has an ester residue consisting of an alkyl group having 1 to 5 carbon atoms, preferably 1 to 4 carbon atoms. When the ester residue has 3 or more carbon atoms, May be linear or branched.
Among the (meth) acrylic acid lower alkyl esters, ethyl acrylate, methyl methacrylate and butyl acrylate are preferable because they easily adjust the glass transition temperature of the polymer to 15 to 40 ° C. and are easily available. When a (meth) acrylic acid ester having an alkyl group having 6 or more carbon atoms is used instead of the (meth) acrylic acid lower alkyl ester, the glass transition temperature of the polymer becomes low, and blocking occurs.

To make the polymers of this invention, acrylonitrile is used in the polymerization in an amount of 1 to 10% by weight, preferably 2 to 8% by weight, based on the total weight of the monomers.
When acrylonitrile is used in an amount less than the above range, the effect of adding acrylonitrile is not exhibited, and the resulting polymer causes blocking or is brittle. Further, when acrylonitrile is used in an amount larger than the above range, the rate of the copolymerization reaction is slow and it is not practical.

To make the polymers of this invention, the comonomer may not be used in the polymerization, but may be used if desired. The amount of the comonomer used varies depending on the comonomer, but is 30% by weight or less, preferably 15% by weight or less, based on the total weight of the monomers. The copolymerizable monomer is particularly preferably a monomer having one or more polymerizable double bonds copolymerizable with (meth) acrylic acid, (meth) acrylic acid lower alkyl ester and acrylonitrile. There is no limit,
For example, (meth) acrylic acid long-chain alkyl ester,
At least one selected from acrylamide, vinyl chloride, vinylidene chloride, vinyl acetate, styrene, butadiene and the like is used.

As the copolymerizable monomer, (meth) acrylic acid long chain alkyl ester is used in an amount of 1 based on the total weight of the monomers.
When used in the polymerization in an amount of -15% by weight, preferably 2-7% by weight, the release property of the surface of the polymer of the present invention is improved and the blocking resistance is further improved. If it is less than the above range, the effect of addition is not particularly recognized, and if it exceeds the above range, whitening occurs, transparency may be deteriorated, and appearance may be deteriorated.
(Meth) acrylic acid long-chain alkyl ester has an ester residue consisting of an alkyl group having 18 to 30 carbon atoms, preferably 18 to 24 carbon atoms, and this ester residue may be linear or branched. Good. Among the (meth) acrylic acid long-chain alkyl esters, stearyl acrylate and behenyl acrylate are preferable because they are easily available and have a large effect. When a (meth) acrylic acid ester having an alkyl group having 12 to 16 carbon atoms is used instead of the (meth) acrylic acid long-chain alkyl ester, no improvement in surface releasability is observed.

The polymer of the present invention is obtained by copolymerizing (meth) acrylic acid, (meth) acrylic acid lower alkyl ester, and acrylonitrile, or is used as the above-mentioned copolymerization monomer. It is also obtained by copolymerizing a monomer. The combination and amount of the monomers used for the polymerization are appropriately selected so that the resulting polymer has an acid value in the above range, a number average molecular weight in the above range and a glass transition temperature in the above range. Combinations and amounts of such monomers are, for example:

To give alkali solubility, methacrylic acid was used to adjust the acid value to 150 mgKOH / g.
The case where the acrylonitrile and ethyl acrylate are used in combination to prepare the alkali-soluble polymer of the present invention as a ternary copolymer will be described as an example. Generally, the homopolymers A, B of the components (monomers) constituting the copolymer,
C, the glass transition temperature of _{··· Tg a, Tg b, Tg} c,
If the (unit: K] is known, the glass transition temperature Tg of the copolymer can be approximately calculated by the following equation.

[0016]

[Equation 1]

[However, a, b, c, ... Are weight fractions of the respective components A, B, C ,.
.. = 1. ] In the formula (*), the components A, B, C
Are methacrylic acid, acrylonitrile, and ethyl acrylate, respectively, and homopolymers of these components,
That is, polymethacrylic acid, polyacrylonitrile,
The glass transition temperatures of polyethyl acrylate are Tg _a = 501K, Tg _b = 398K, and Tg _c = 2, respectively.
It is 49K. The amount of methacrylic acid required to obtain a copolymer having an acid value of 150 mgKOH / g was calculated and
= 0.23. The amount of acrylonitrile is 1 to 10% by weight, preferably 2 to 8% by weight, and if an appropriate value is selected within this range, for example, 7% by weight, b =
It is 0.07. At this time, the amount of ethyl acrylate is c = 0.70. Therefore, the alkali-soluble polymer of the present invention obtained by copolymerizing 23% by weight of methacrylic acid, 7% by weight of acrylonitrile, and 70% by weight of ethyl acrylate has the following formula (*):

[0018]

[Equation 2]

It becomes The glass transition temperature of the alkali-soluble polymer actually obtained in this manner was actually measured by differential scanning calorimetry, and Tg = 24 ° C., and the acid value was actually measured to be 152 mgKOH / g. The polymer of the present invention generally has a glass transition temperature several degrees to ten degrees higher than the calculated value obtained from the above formula (*), and has an acid value almost equal to the calculated value. Further, although the glass transition temperature can be estimated by the calculation as described above, those having a glass transition temperature of 15 to 40 ° C. in the measured value were flexible and did not cause blocking.

Polymerization for obtaining the polymer of the present invention may be solution polymerization, non-aqueous dispersion polymerization, bulk polymerization, emulsion polymerization, suspension polymerization and the like. In order to obtain the polymer of this invention, since the amount of (meth) acrylic acid used is large, solution polymerization, non-aqueous dispersion polymerization, bulk polymerization are preferable, and acrylic acid or acrylic acid ester in which the polymerization reaction tends to runaway is preferably used. Since it is used, the solution polymerization and the non-aqueous dispersion polymerization, which are easy to thermally control the polymerization, are more preferable, and the solution polymerization is more preferable in that there is no contamination.

The solvent used for the solution polymerization is not particularly limited as long as it is a liquid capable of dissolving both the above-mentioned monomer for obtaining the polymer of the present invention and the produced polymer of the present invention.
Examples thereof include aliphatic alcohols having 1 to 3 carbon atoms such as methanol, ethanol and glycol; polar organic solvents such as cyclic ethers such as tetrahydrofuran.

The solvent used for the non-aqueous dispersion polymerization can dissolve the above-mentioned monomers for obtaining the polymer of the present invention,
And, the produced polymer of the present invention is not particularly limited as long as it is a liquid insoluble, for example, benzene, toluene,
Examples include non-polar organic solvents such as liquid hydrocarbons such as hexane and cyclohexane. The amount of the solvent used for the solution polymerization or the non-aqueous dispersion polymerization is preferably 20 to 70% by weight, and 30 to 60% by weight based on the total weight of the monomers.
Weight percent is more preferred. If it is less than the above range, stirring may be insufficient due to thickening at the end of polymerization, and if it exceeds the above range, the molecular weight of the polymer produced may not be increased to the above range.

The polymerization initiator used to obtain the polymer of the present invention is an azo initiator such as azobisisobutyronitrile, an organic peroxide such as benzoyl peroxide, and the like. Normally, for total weight,
It is used in a proportion of 0.001 to 1.0% by weight. Monomers and polymerization initiators used to obtain the polymer of the present invention, respectively, may be charged to the polymerization reactor before the polymerization, the whole amount thereof, or a part thereof to the polymerization reactor before the polymerization. The rest of the charge is once during the polymerization, or continuously, or
You may supply in multiple times.

The polymerization for obtaining the polymer of the present invention is carried out at a temperature of 50 to 80 ° C. for 2 to 20 hours. The end of polymerization is
Generally, the polymerization rate is 85 to 100%, preferably 90 to 10
It is the time when it reaches 0%. If the polymerization rate is out of the above range, the high boiling point monomer may not be completely removed in the devolatilization step. The number average molecular weight of the polymer to be produced is almost determined by the type of the monomer, the polymerization temperature, the concentration of the monomer and the polymerization initiator, and therefore the polymerization is carried out by appropriately selecting them so that the number average molecular weight falls within the above range. .

After the completion of the polymerization, volatile components such as unreacted monomers and solvents are removed from the reaction mixture and, if necessary, the polymer is purified by a known polymer washing method to obtain the polymer of the present invention. The obtained polymer is a colorless to white solid at room temperature (25 ° C.) and can be in the form of pellets, powder, granules and the like. The polymer of the present invention thus obtained has a constitutional unit derived from (meth) acrylic acid, (meth) acrylic acid lower alkyl ester, acrylonitrile and a copolymerizable monomer in an amount of 10 to 25% by weight, respectively. ,
50-89% by weight, 1-10% by weight, 0-30% by weight,
Preferably 14 to 23% by weight, 60 to 80% by weight, 2 to
8% by weight, 0 to 15% by weight, and the main chain is composed of linear chains in which these constituent units are randomly arranged.
In the polymers of this invention, the amounts of these constituent units are the same or nearly the same as the composition of the monomer components used in the polymerization.

Since the polymer of the present invention does not cause blocking, it is not necessary to add a lubricant to prevent blocking. Therefore, whitening due to the lubricant does not occur. Since the polymer of the present invention is flexible and has excellent strength, it is not necessary to add a plasticizer. Therefore, the plasticizer does not cause strength deterioration or sticking. The polymer of the present invention has alkali solubility, is flexible and excellent in strength, and does not cause blocking, so that there is no problem in handling even when transported in pellet form, and it can be wound into a roll shape even when formed into a film. It can be handled and used for applications such as packaging.

Since the polymer of the present invention has a film forming ability, it can be formed into a film by a usual film forming method. As a film forming method, for example, an inflation method, a T-die method, a calender method, a hot press method, a casting method or the like can be used. The inflation method and the T-die method are suitable for the polymer of the present invention because they are widely used industrially and do not use a solvent or the like.

In the inflation method, T-die method, calender method, and hot press method, the polymer of the present invention is melted and molded. In the casting method, a polymer is dissolved in a solvent capable of dissolving the polymer of the present invention, spread on a coating object or a mold, and dried to form a film, thereby forming a film. The solvent used is, for example, a solvent that can be used in the above solution polymerization.

When the polymer of the present invention is formed into a film,
Although only the polymer of the present invention may be used, an additive may be added to the polymer if necessary. Such additives include, for example, inorganic fillers such as kaolin, mica, talc, etc., and may be 0 based on the total weight of the polymer.
It is added in a proportion of 50% by weight. The obtained film has, for example, a thickness of 50 to 200 μm, is tough, does not cause blocking, and can be dissolved in a basic liquid.

The basic liquid capable of dissolving the polymer and film of the present invention is, for example, aqueous ammonia, sodium carbonate aqueous solution, sodium hydrogen carbonate aqueous solution, sodium hydroxide aqueous solution, and is appropriately selected according to the intended use of the polymer. It The term "polymer is soluble in a basic liquid" means that the polymer can be completely dissolved in a basic liquid by an operation of adding the polymer to 0.2% aqueous ammonia and stirring. Is.

[0031]

The polymer of the present invention has an acid value of 80 mgKOH / g or more and is therefore alkali-soluble, and moreover 200 mgKO
It does not absorb moisture under normal conditions because it has an acid value of H / g or less. Since the polymer of the present invention has a number average molecular weight of 10,000 or more, the mechanical strength of the polymer is sufficiently high and it can be used as a film having high strength. Further, since the polymer has a number average molecular weight of 300,000 or less. , Easy to form into a film.

The polymer of the present invention has a temperature of 15 ° C. or higher and 40 ° C.
Since it has the following glass transition temperature, it is soft and easy to process and can be formed into a film. To produce the polymer of this invention, (meth) acrylic acid is used in the polymerization in an amount of 10 to 25% by weight to produce a polymer of 8%.
It has an acid value of 0 mgKOH / g or more and is soluble in alkali.

In order to prepare the polymer of the present invention, a lower alkyl group-containing (meth) acrylic acid ester is used in the polymerization in an amount of 50 to 89% by weight so that the resulting polymer has alkali solubility. And (meth) acrylic acid can be copolymerized, and the resulting polymer has film-forming ability. To make the polymer of this invention, acrylonitrile is used in the polymerization in an amount of 1-10% by weight,
The polymer produced does not have tackiness that causes blocking, and is flexible and has excellent strength.

When a long-chain alkyl group-containing (meth) acrylic acid ester is used as a copolymerization monomer in an amount of 1 to 15% by weight, the blocking resistance of the resulting polymer is further enhanced. The polymer film of the present invention does not cause blocking, has excellent strength, is flexible and transparent, and can be dissolved in a basic liquid.

[0035]

EXAMPLES Examples of the present invention and comparative examples outside the scope of the present invention will be shown below, but the present invention is not limited to the following examples. In the following, "parts" means "parts by weight" and "%" means "% by weight" unless otherwise specified. (Example 1) A reactor equipped with a stirrer, a thermometer, and a condenser was charged with 72 parts of ethyl acrylate and 19 parts of methacrylic acid.
Parts, acrylonitrile 4 parts, stearyl acrylate 5
Part, methanol 150 parts, and azobisisobutyronitrile 0.25 part were introduced to sufficiently substitute nitrogen, and then the mixture was heated in a water bath at 68 ° C. to initiate polymerization.

At an internal temperature of about 65 ° C., the mixture was refluxed, the polymerization proceeded extremely stably, and the polymerization was completed in about 9 hours.
The polymerization rate was 95%. The reaction mixture obtained is 160
It was heated to ˜180 ° C., devolatilized using a devolatilizing extruder whose pressure was reduced to 1 Torr or less, extruded into a rope shape, and cut into a length of several millimeters to obtain a pellet-shaped polymer. (Examples 2 to 8 and Comparative Examples 1 to 5) Monomers used,
The procedure of Example 1 was repeated except that the amount and the polymerization time were changed as shown in Tables 1 and 2 to obtain a polymer in pellet form.

Example 9 The same operation as in Example 1 was repeated except that the polymerization time was changed to 4 hours, the amount of methanol was changed to 43 parts, and the amount of azobisisobutyronitrile was changed to 0.072 part. Got united. However, when the stirring became difficult, the heating was stopped and the polymerization was stopped.

Comparative Example 6 In Example 1, the polymerization time was 2 hours and the amount of azobisisobutyronitrile was 2.5.
The same operation was performed except that the part was changed to obtain a polymer in pellet form.

[0039]

[Table 1]

[0040]

[Table 2]

Example 10 The polymer obtained in Example 1 was heated at a barrel temperature of 180 using an inflation device.
C., extrusion at a die jacket temperature of 180.degree. C. (linear velocity of 5 m / min), blow ratio of 2.0, and take-off speed of 10 m / min to obtain a slightly translucent film having a film thickness of about 30 .mu.m. However, a circular die having a diameter of 4 inches, a mold width of 20 mils, and a length of 160 mils was used, and dry air was used for expansion.

Example 11 The polymer obtained in Example 1 was formed into a film by using a small extrusion kneader. This extrusion kneader has two heating areas, a melting part and a slit nozzle, and can extrude the melting part to form a film or the like. Wide slit nozzle (40mm x
0.2 mm) and heat to 170-190 ℃, about 50
A film having a thickness of about 50 μm was obtained by applying a load of ˜70 gf.

(Example 12 and Comparative Example 7) A film was obtained by repeating the procedure of Example 11 except that the polymer used and the temperature for film formation were changed as shown in Tables 3 and 4. For the polymers obtained in the above Examples and Comparative Examples, number average molecular weight, weight average molecular weight, polydispersity (molecular weight distribution), acid value, glass transition temperature, solubility, blocking resistance, flexibility, strength, surface The property was examined. The results are shown in Table 3 ~
Shown in FIG.

The number average molecular weight, weight average molecular weight and polydispersity index were measured by gel permeation chromatography. The acid value was measured by a titration method with potassium hydroxide, and expressed as the number of milligrams of potassium hydroxide required to neutralize 1 gram of the polymer. The glass transition temperature was measured by differential scanning calorimetry.

The solubility was shown based on the time taken for the film-shaped polymer to dissolve in alkali. Specifically, 0.2
% Ammonia water (pH 11-12) in a 100 ml container, put a film (0.1 g) with a thickness of 50 μm cut into 35 mm x 50 mm, and apply ultrasonic waves at room temperature to determine the time to dissolve as follows. did. A: Dissolution time 5 minutes or more, less than 15 minutes B: Dissolution time 15 minutes or more, less than 30 minutes C: Dissolution time 30 minutes or more, less than 60 minutes D: Dissolution time 60 minutes or more, less than 120 minutes E: Dissolution time 120 minutes The 0.2% -Na ₂ CO ₃ aqueous solution and pure water were also measured and judged in the same manner.

Blocking resistance was determined by cutting a film having a thickness of 50 μm into a size of 20 mm × 20 mm to prepare a test piece, stacking four test pieces, sandwiching them between glass plates, and applying a load of 1 kgf to the test piece.
After standing for 2 days in the atmosphere at 50 ° C and 50% relative humidity, the following judgment was made. 5: There is no close contact. 3: Adheres closely, and when peeled off, the test piece is deformed and peeled off. 1: It cannot be peeled off at all. 4: Adhesion is about halfway between 5 and 3 above (can be peeled off very easily). 2: Adhesion between the above 3 and 1 is close (the test piece is about to break when peeled off and barely peels off).

As for flexibility, a film having a thickness of 50 μm is 30
A test piece was prepared by cutting into a size of 200 mm × 200 mm, and the test piece was examined by using a table having two horizontal planes with a height difference of 50 mm and arranged stepwise. The test piece was placed on the upper horizontal surface of this table, and the test piece was arranged so that the length direction of the test piece was orthogonal to the end of the upper horizontal surface. The test piece is moved slowly so that one end in the lengthwise direction of the test piece projects 60 mm from the end of the upper horizontal surface, and the distance when one end of the test piece reaches the lower horizontal surface (the end of the upper horizontal surface Was projected in the vertical direction on the lower horizontal plane, and the shortest distance from this projected line to the position where one end reached) was measured and determined as follows. A: Reaching distance is less than 15 mm B: Reaching distance is 15 mm or more and less than 25 mm C: Reaching distance is 25 mm or more Strength is 50 mm thick film cut into 30 mm x 10 mm to make a test piece, chuck distance 10 mm, test Speed 1
A tensile test was carried out by applying a tensile force to the film at a rate of 00 mm / min along the extrusion direction, and the tensile force when the film broke was measured [unit: kgf / mm ² ].

Regarding the surface texture, a film with a thickness of 50 μm
Cut into 0 mm x 20 mm to make a test piece, measure the haze (%) according to JIS K-6714 with an integrating turbidimeter,
Further, the smoothness was visually compared.

[0049]

[Table 3]

[0050]

[Table 4]

As shown in Tables 3 and 4, although the polymers of Examples, which are the polymers of the present invention, are soluble in the basic liquid,
It did not dissolve in neutral or acidic liquids, did not cause blocking, was flexible and had excellent strength, and did not whiten. In the polymer of Comparative Example 1, since the amount of the lower alkyl group-containing (meth) acrylic acid ester used was too large, the amount of the (meth) acrylic acid used was inevitably low, and the acid value was low, so The solubility was poor. In the polymer of Comparative Example 2, the amount of (meth) acrylic acid used was too large, and when left to stand, the surface became sticky due to moisture, blocking was likely to occur, and flexibility was small and hard and brittle. Comparative Example 3
Since the polymer of (1) used a long-chain alkyl group-containing (meth) acrylic acid ester instead of acrylonitrile, it had poor blocking resistance. The polymer of Comparative Example 4 was inferior in actual polymerization because the amount of acrylonitrile used was too large, resulting in a slow polymerization rate and a long reaction time. In the polymer of Comparative Example 5, the amount of the long-chain alkyl group-containing (meth) acrylic acid ester used was too large.
The transparency deteriorated, the surface condition deteriorated, and it was mechanically fragile. Since the polymer of Comparative Example 6 had a number average molecular weight of less than 10,000, it could not be formed into a film having sufficient strength.

[0052]

The alkali-soluble polymer of the present invention does not cause blocking, is flexible and has excellent strength.
It is easy to handle as a molding material such as a film, and is useful for producing a molded product such as an excellent alkali-soluble film. The polymer of this invention does not require the addition of a lubricant to prevent blocking, and does not require the addition of a plasticizer to eliminate brittleness.

The film of the polymer of the present invention does not cause blocking, is excellent in strength, is flexible and transparent, and easily dissolves in a basic liquid. It is useful as a protective film, a base material for labels, a film for separating and storing for a short time (for example, an agricultural film, a film for packaging laundry).

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display area C08F 220: 44) C08L 33:06

Claims (3)

[Claims] 1. At least one of acrylic acid and methacrylic acid, 10 to 25% by weight, an acrylate ester having an alkyl group having 1 to 5 carbon atoms and an alkyl group having 1 to 5 carbon atoms. 50 to 89% by weight of at least one methacrylic acid ester, 1 to 10% by weight of acrylonitrile, and 0 to 30% by weight of another unsaturated monomer copolymerizable with these monomers. An alkali-soluble polymer having an acid value of 80 to 200 mgKOH / g, a number average molecular weight of 10,000 to 300,000, and a glass transition temperature of 15 to 40 ° C., which is obtained by polymerizing the components. 2. The other unsaturated monomer has 1 carbon atom.
1 to 15% by weight of at least one of an acrylic acid ester having 8 to 30 alkyl groups and a methacrylic acid ester having an alkyl group having 18 to 30 carbon atoms
The alkali-soluble polymer according to claim 1, which comprises. 3. The alkali-soluble polymer according to claim 1, which is a film.