JP2003155307A - Resin for melt molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a resin for melt molding having excellent long-run moldability. SOLUTION: This oxyalkylene group-containing polyvinyl alcohol-based resin is obtained by saponifying an oxyalkylene group-containing vinyl ester- based copolymer which is obtained by copolymerization while feeding an oxyalkylene group-containing monomer, a vinyl ester monomer and a polymerization catalyst to a polymerization system by a continuous drip or a multifractionated drip.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a melt molding resin comprising an oxyalkylene group-containing polyvinyl alcohol-based resin whose physical properties are improved by a specific polymerization formulation, and more particularly to long-run moldability during melt molding. It relates to an excellent melt-molding resin.

[0002]

2. Description of the Related Art Conventionally, an oxyalkylene group-containing polyvinyl alcohol-based resin has been known as a melt-molding resin, and the applicant of the present invention also has a specific aqueous solution viscosity and methanol as a resin having good moldability. Soluble content 5% by weight
The following oxyalkylene group-containing polyvinyl alcohol resins have been proposed (JP-A-4-298535 and JP-A-5-310955).

[0003]

As one of the means, such a technique is to thoroughly wash an oxyalkylene group-containing polyvinyl alcohol resin with methanol or the like to remove low-saponified products and highly modified products in the resin. Although it was attempted to improve the moldability of the resin, a considerable improvement in moldability was recognized, but during long run molding for 70 hours or more, especially when molding the film at a high speed of about 100 m / min. However, it was found that the thickness of the edges of the ears varies, and further improvement has become necessary.

[0004]

In view of such circumstances, the present inventor has made earnest studies on a method for producing an oxyalkylene group-containing polyvinyl alcohol-based resin, particularly a polymerization formulation of an oxyalkylene group-containing vinyl ester. An oxyalkylene group-containing product obtained by saponifying an oxyalkylene group-containing vinyl ester-based copolymer obtained by copolymerizing an alkylene group-containing monomer, a vinyl ester monomer and a polymerization catalyst into a polymerization system while continuously dropping or multi-dividing It was found that a polyvinyl alcohol-based resin can solve the above problems, and the present invention has been completed.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.

The oxyalkylene group in the oxyalkylene group-containing polyvinyl alcohol resin of the present invention is represented by the following general formula (1).

[Chemical 1] (However, R ₁ and R ₂ are hydrogen or an alkyl group, R ₃ is hydrogen,
An alkyl group, an alkyl ester group or an alkyl amide group, and n represents an integer. )

In the above general formula (1), the number of n, that is, the average chain length of the oxyalkylene group is preferably 2 to 300, more preferably 5 to 300, especially 5 to 100, especially 5.
-60. If the average chain length is out of this range, a part of the resin may be decomposed during melt-molding, which may cause coloring or an offensive odor, which is not preferable. Specific examples of the oxyalkylene group include a polyoxyethylene group, a polyoxypropylene group, and a polyoxybutylene group.

Examples of the monomer having an oxyalkylene group are as follows. However, the present invention is not limited to these. [(Meth) acrylic acid ester type] It is represented by the following general formula (2), and specific examples thereof include polyoxyethylene (meth) acrylate and polyoxypropylene (meth) acrylate.

[Chemical 2] (However, R is hydrogen or a methyl group, A is any one of an alkylene group, a substituted alkylene group, a phenylene group and a substituted phenylene group, m is an integer of 0 or 1 or more, R ₁ , R ₂ , R ₃ and n are the above-mentioned. same as.)

[(Meth) acrylic acid amide type] A compound represented by the following general formula (3), specifically polyoxyethylene (meth) acrylic acid amide, polyoxypropylene (meth) acrylic acid amide, polyoxyethylene (meth) acrylic acid amide, Oxyethylene (1-
(Meth) acrylamide-1,1-dimethylpropyl)
Esters and the like can be mentioned.

[Chemical 3] (However, A, m, R, R ₁ , R ₂ , R ₃ , and n are the same as above, and R ₄ is hydrogen or one represented by the general formula (1).)

[(Meth) allyl alcohol type] A compound represented by the following general formula (4), and specific examples thereof include polyoxyethylene (meth) allyl ether and polyoxypropylene (meth) allyl ether.

[Chemical 4] (However, R, R ₁ , R ₂ , R ₃ , and n are the same as above.)

[Vinyl ether type] The following general formula (5)
And specifically include polyoxyethylene vinyl ether, polyoxypropylene vinyl ether, and the like.

[Chemical 5] (However, A, R ₁ , R ₂ , R ₃ , m, and n are the same as above.) Among these oxyalkylene group-containing monomers, the (meth) allyl alcohol type monomer represented by the general formula (4) is preferable. Used for. In addition to these, tetrahydrofurfuryloxy polyalkylene oxide alkenyl ether and polyalkylene oxide alkenyl ether can be mentioned.

Further, vinyl ester monomers copolymerizable with the above monomers include vinyl formate, vinyl acetate,
Vinyl trifluoroacetate, vinyl propionate, vinyl butyrate, vinyl caprate, vinyl laurate, vinyl versatate, vinyl palmitate, vinyl stearate, vinyl pivalate, etc. are used alone or in combination, but industrially Vinyl acetate is preferred.

The polyvinyl alcohol resin of the present invention is
50 mol% or less of a general monomer other than the oxyalkylene group-containing monomer and the vinyl ester monomer described above may be coexistent within a range not impairing the object of the present invention. These monomers are exemplified below. [Ethylenically Unsaturated Carboxylic Acid and Its Alkyl Ester, etc.] Methyl crotonate, ethyl crotonate, methyl itaconate, ethyl itaconate, methyl sorbate, ethyl sorbate, maleic acid monoalkyl ester, maleic acid dialkyl ester, oleic acid Alkyl ester, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, pentyl (meth) acrylate, heptyl (meth) acrylate, (meth) acrylic acid Examples include octyl, decyl (meth) acrylate, hexadecyl (meth) acrylate, and octadecyl (meth) acrylate.

[Allyl ester of saturated carboxylic acid] Allyl stearate, allyl laurate, allyl coconut oil fatty acid, allyl octylate, allyl butyrate and the like. [Α-Olefin] Ethylene, propylene, α-hexene, α-octene, α-decene, α-dodecene, α-hexadecene, α-octadecene and the like. [Ethylenically unsaturated carboxylic acid] (meth) acrylic acid,
Crotonic acid, (anhydrous) maleic acid, fumaric acid, itaconic acid and their alkali metal salts, ammonium salts and the like.

[Alkyl vinyl ether] Propyl vinyl ether, butyl vinyl ether, hexyl vinyl ether, octyl vinyl ether, decyl vinyl ether, dodecyl vinyl ether, tetradecyl vinyl ether, hexadecyl vinyl ether, octadecyl vinyl ether and the like.

[Alkyl allyl ether] Propyl allyl ether, butyl allyl ether, hexyl allyl ether, octyl allyl ether, decyl allyl ether, dodecyl allyl ether, tetradecyl allyl ether, hexadecyl allyl ether, octadecyl allyl ether and the like. Others, (meth) acrylamide, (meth) acrylonitrile, (meth) allyl sulfonate,
It is also possible to use an ethylenically unsaturated sulfonate, styrene, vinyl chloride, a thiol chain transfer agent containing an amino group, an ammonium group, a carboxyl group, a sulfonic acid group, or the like.

The polyvinyl alcohol resin of the present invention is
Oxyalkylene group obtained by copolymerizing the above-mentioned oxyalkylene group-containing monomer, vinyl ester monomer and polymerization catalyst into the polymerization system while continuously dropwise charging or multi-divided charging (hereinafter, collectively referred to as divided charging). A saponified vinyl ester-based copolymer,
First, a method for producing such an oxyalkylene group-containing vinyl ester-based copolymer will be specifically described.

Such a production method is characterized in that during the copolymerization, the copolymerization monomer and the polymerization catalyst are separately charged into a polymerization system (specifically, a polymerization vessel, a reaction vessel or the like) and the copolymerization is carried out. The amount of each of the charged monomers is preferably 30 to 99% by weight (more preferably 40 to 99% by weight, particularly 50 to 97% by weight, particularly 65 to 95% by weight) based on the total amount of the charged monomers.

If the amount of the monomer is less than 30% by weight,
There is a possibility that the obtained molded product may not exhibit sufficient strength, which is not preferable. On the contrary, when it exceeds 99% by weight, it is necessary to raise the melting temperature during the melt molding, which may cause thermal decomposition, which is not preferable.

When the monomers are separately charged, the oxyalkylene group-containing monomer and the vinyl ester monomer may be separately charged separately, or may be separately charged as a mixture of both monomers. However, it is preferable because the ratio of both monomers can be easily controlled. In addition, the charging method of the monomers other than the above is not particularly limited, and it is possible to mix and charge with the vinyl ester monomer, charge all at once, or separately charge separately.

The molar ratio of the oxyalkylene group-containing monomer and the vinyl ester monomer at the time of divided charging is not particularly limited, but it is 0.1 / 100 to 10/100 (further 0.5 / 100 to 5/100, particularly preferably 1/100 to 4 /
100) is preferable, and by controlling such a molar ratio, a polyvinyl alcohol-based resin containing 0.1 to 10 mol% of an oxyalkylene group is finally obtained.

When the amount of modification by the oxyalkylene group is less than 0.1 mol%, the melting point of the melt-molding resin becomes high and the difference from the thermal decomposition temperature disappears, which may lead to thermal decomposition during melt molding. If it exceeds 10 mol%, thermal decomposition tends to occur, which is not preferable.

In copolymerizing the above monomers,
The polymerization catalyst is not particularly limited, but it is carried out by using a known radical polymerization catalyst such as azobisisobutyronitrile, acetyl peroxide, benzoyl peroxide, lauroyl peroxide, etc. Such a catalyst is usually dissolved in an organic solvent and charged. Be done.

In the present invention, it is also necessary to charge such a polymerization catalyst into the polymerization system in a divided charge. The amount of the polymerization catalyst to be charged separately is 10 to 99% by weight of the total amount charged.
(Further, 10 to 90% by weight, particularly 15 to 90% by weight, especially 15 to 85% by weight) is preferable, and if the amount is less than 10% by weight, the strength of the obtained molded article decreases, and If it exceeds 99% by weight, the melt viscosity at the time of melt molding becomes high, which is not preferable.

The polymerization catalyst is supplied to the polymerization system by continuous dropping or multi-division charging. The continuous charging or the division charging of the polymerization catalyst is carried out simultaneously with the continuous charging or the division charging of the monomers. Continuous charging or divided charging into the system may be started, or it may be started before or after continuous charging or divided charging of monomers, but preferably a method of performing continuous charging or divided charging at the same time is adopted. To be done.

Further, in the present invention, when the polymerization catalyst is continuously dropped or multi-divided, it is preferable to carry out the continuous dropping, but in the case of multi-divided charging, three times or more (more preferably four times or more, particularly preferably). 5 times or more, especially 6 times or more)
Is preferably divided into multiple parts. If the number of times is 2 or less, the effect of the present invention may not be sufficiently obtained, which is not preferable. The continuous dropping method also includes an intermittent continuous dropping method.

Further, the divided charging time (polymerization reaction time) of the monomers and the polymerization catalyst is not particularly limited, but is about 4 to 24 hours, and if necessary, 1 time before starting the divided charging of the monomers and the polymerization catalyst. ~ 120 minutes of aeration (oxygen expulsion)
In order to polymerize the unreacted residual oxyalkylene group-containing monomer or vinyl ester monomer after completion of the step and divided charging, a polymerization step of about 1 to 360 minutes may be provided.

The charging rate of the monomers and the polymerization catalyst to be additionally charged is preferably constant, but can be changed. Further, the method of charging monomers and a polymerization catalyst to be additionally charged into the system is not particularly limited, but a method of charging by a shower method, a method of mixing by mixing with a condenser reflux liquid, a method of charging directly by pouring can be mentioned. . Further, the monomers to be additionally charged may be charged into the system as they are, but may be mixed with a solvent such as methanol and charged. Further, the polymerization catalyst to be additionally charged can be dissolved in a solvent and charged.

The oxyalkylene group-containing vinyl ester copolymer thus obtained is then saponified.

In the saponification, the copolymer is dissolved in alcohol, in some cases benzene, methyl acetate and the like (including mixed solvent), and saponification is carried out in the presence of a saponification catalyst. Examples of alcohols include methanol, ethanol, butanol and the like. The concentration of the copolymer in alcohol is preferably 20 to 70% by weight, more preferably 20 to 70% by weight.
To 50% by weight.

As the saponification catalyst, it is preferable to use an alkali metal hydroxide such as sodium hydroxide, potassium hydroxide, sodium methylate, sodium ethylate or potassium methylate, or an alkali catalyst such as alcoholate. It is necessary to use the catalyst in an amount of 1 to 100 mmol% based on the vinyl ester monomer. Further, water can be added to the saponification reaction system, if necessary. It is also possible to carry out the saponification reaction using an acid catalyst such as sulfuric acid or hydrochloric acid.

The degree of saponification at this time is preferably 80 mol% or more (more preferably 88 mol% or more, particularly 98 mol% or more). If the saponification degree is less than 80 mol%, the odor of acetic acid will be generated during melt molding. It is not desirable to occur. The degree of saponification as used herein means the ratio of the vinyl acetate component of the vinyl ester copolymer containing an oxyalkylene group converted into a hydroxyl group in mol%.

After the saponification, since the particles of the polyvinyl alcohol resin are dispersed in the saponification solvent, it can be obtained in the form of powder or industrially.

The average degree of polymerization of the obtained oxyalkylene group-containing polyvinyl alcohol-based resin is preferably 300 or more (further 300 to 2000, particularly 400 to 800), and when the average degree of polymerization is less than 300, the obtained molded product is obtained. Is not preferable because the impact resistance of is lowered. The average degree of polymerization is measured according to JIS K 6726.

Thus, an oxyalkylene group-containing polyvinyl alcohol resin useful for melt molding can be obtained. When using such an oxyalkylene group-containing polyvinyl alcohol-based resin for melt molding, a saturated aliphatic amide (for example, stearic acid amide), an unsaturated fatty acid amide (for example, oleic acid amide), a bis Fatty acid amide (for example, ethylenebisstearic acid amide), fatty acid metal salt other than the above (for example, calcium stearate, magnesium stearate, zinc stearate, etc.), low molecular weight polyolefin (for example, low molecular weight of about 500 to 10,000). Lubricants such as molecular weight polyethylene or low molecular weight polypropylene), inorganic salts (for example, hydrotalcites described later), plasticizers (for example, aliphatic polyhydric alcohols such as ethylene glycol, glycerin, and hexanediol), oxygen Absorbent (eg reduced iron Inorganic oxygen absorbers such as powders and potassium sulfite, organic compound oxygen absorbers such as ascorbic acid, hydroquinone and gallic acid, and polymer oxygen absorbers), heat stabilizers, light stabilizers, antioxidants Agent (for example, "IR manufactured by Ciba Specialty Chemicals"
GANOX1098 ", etc.), UV absorbers, colorants,
Antistatic agent, surfactant, antibacterial agent, deodorant (eg, activated carbon), anti-blocking agent (eg, talc particles), slip agent (eg, amorphous silica particles), filler (eg, inorganic material) (Filler etc.) etc. may be blended.

By subjecting the oxyalkylene group-containing polyvinyl alcohol resin to melt molding, a desired molded article can be obtained. The shape of the molded article is a film, sheet, tape, bottle, pipe. Examples of the shape, filament, and atypical cross-sectional shape and various injection-molded products can be mentioned. To obtain the effect of the present invention more remarkably, melting of a hollow container such as a film, a sheet, or a bottle is required. A molded product is preferable, and such a melt-molded product will be further described, but the present invention is not limited thereto.

The oxyalkylene group-containing polyvinyl alcohol resin can be melt-extruded and melt-extrusion coated (coated) on another substrate. Examples of such a substrate include paper, hydrolyzed paper, metal foil, and Examples include stretched, uniaxially or biaxially stretched plastic films or sheets, and inorganic substance vapor-deposited bodies thereof, woven fabrics, non-woven fabrics, metallic cotton, wood, and the like.

It is also possible to laminate a film or sheet-shaped melt-molded product with the above-mentioned base material via an adhesive as described above, but the water-solubility of the melt-molded product or the base material is taken into consideration. It is also preferable to choose a water-soluble adhesive.

Furthermore, it is also possible to stretch the melt-formed product once formed into a film or sheet, and as the stretching method, there are a roll stretching method, a tenter stretching method, a tubular stretching method, a stretching blow method and the like. Among draw forming, vacuum pressure forming and the like, one having a high draw ratio can be adopted. In the case of biaxial stretching, either simultaneous biaxial stretching method or sequential biaxial stretching method can be adopted. The stretching temperature is selected from the range of 60 to 170 ° C, preferably about 80 to 160 ° C.

After the stretching is completed, it is also possible to carry out heat setting, and such heat setting can be carried out by a well-known means.
The heat treatment may be performed at 70 ° C., preferably 100 to 160 ° C. for about 2 to 600 seconds.

When manufacturing a hollow container, it can be molded using an extrusion blow molding machine.
A hollow container can be manufactured by sandwiching a tubular parison extruded from an extruder in a blow mold, blowing air from the inside of the tube to inflate the parison, and closely contacting the parison with the mold. The heating temperature of the parison at this time is 180
The mold temperature at the time of blowing is 50 to 1 from the range of ~ 250 ° C.
Each can be selected from the range of 00 ° C.

Thus, a melt-molded product is obtained. Such a molded product, particularly a film- or sheet-shaped molded product, is used for packaging solid medicine such as detergents and agricultural chemicals, pet-related applications such as excrement disposal bags, and disposable diapers. It can be used for sanitary products that can be discarded in water and water.

When used for packaging the above-mentioned detergents, pesticides, and other chemicals, the melt-molded product of the present invention formed into a film or sheet may be hermetically packaged. For example, the film may be previously packaged. Leave it in a bag,
Any method such as a method of packaging a drug or a method of directly packaging a drug with the film can be adopted, and a so-called unit package in which a certain amount of the drug is packaged is completed by these methods.

There is no particular limitation on the drug to be provided in such a unit package, and it may be any drug dissolved or dispersed in water and may be alkaline, neutral or acidic. , Specifically, powdered soap, synthetic detergent,
Agricultural chemicals, germicides, deodorants, insecticides and the like can be mentioned.

[0045]

EXAMPLES The present invention will be specifically described below with reference to examples. In the examples, "%" and "parts" mean weight basis unless otherwise specified.

Example 1 A polymerization vessel was charged with 5.8 parts of polyoxyethylene monoallyl ether having an oxyethylene group having an average chain length (n) of 10 and 40 parts of vinyl acetate and 15 parts of methanol, and the mixture was heated to reflux. After warming and refluxing for 30 minutes, azobisisobutyronitrile was charged in a total amount (initial charge + addition charge) of 0.15 mol% with respect to the amount of vinyl acetate to start polymerization.

Then, after polymerizing for 30 minutes, as shown in Table 1, 50 of the above polyoxyethylene monoallyl ether was prepared.
% Methanol solution 8.7 parts (60% of the total charged amount) and vinyl acetate 60 parts (60% of the total charged amount; provided, however, the amount including the vinyl acetate amount used for the azoisobutyronitrile charging described later) and 0.15 mol% of azoisobutyronitrile (relative to the total amount of charged vinyl acetate) was separately charged into the polymerization vessel over 6 hours at a constant rate. At this time, the molar ratio of polyoxyethylene monoallyl ether to be additionally charged and vinyl acetate was always 2.5 / 100. The amount of azobisisobutyronitrile additionally charged is
50% of the total amount of charged azoisobutyronitrile was dissolved in a vinyl acetate / methanol mixed solution (azobisisobutyronitrile / vinyl acetate / methanol = 1/9 /
40 weight ratio), and additional charging was performed. After additional charging 30
The reaction was continued for a minute, and the reaction was stopped by adding a polymerization inhibitor and methanol to obtain a methanol solution of oxyalkylene group-containing polyvinyl acetate. Polymerization rate at this time is 92%
Met.

Next, the liquid is removed from the liquid in a continuous demonomer column until the amount of the residual monomer in the liquid reaches 0.06%, and methanol is added to adjust the polyvinyl acetate concentration to 40%.
Then, 11 mmol% (vs vinyl acetate) sodium hydroxide was added in a methanol solution to saponify (3
5 ° C.) to obtain a polyoxyethylene group-containing polyvinyl alcohol resin as shown in Table 2. Thereafter, sodium acetate is removed by washing with methanol, and the product is dried to give a powdered oxyalkylene group-containing polyvinyl alcohol resin (saponification degree: 98.5 mol%, average polymerization degree: 72).
0) was obtained, the resin was supplied to a single-screw extruder, and film formation was performed under the following conditions to obtain a film having a thickness of 30 μm.

[0049]

With the above-mentioned film formation, the condition of the edge portion of the film obtained after 72 hours was visually observed and the long-run moldability was evaluated according to the following criteria. A: No gel was generated, and no change in film thickness at the end of the ear was observed. B: A slight amount of gel was observed, but no change in film thickness at the end of the end was observed. C ... Many gels were observed, and thickness variation at the edge was also observed

Examples 2 to 4 According to Example 1, under the conditions shown in Table 1, an oxyalkylene group-containing polyvinyl alcohol resin as shown in Table 2 was produced (polymerization rate: about 91%) and carried out. Long-run moldability was evaluated in the same manner as in Example 1.

The method of charging the polymerization catalyst in each example was as follows. Example 2: Initial charging amount / additional charging amount ratio = 0.15 / 0.
15 mol% (vs. total vinyl acetate), 1 additional charge
It was divided into 0 parts, and was charged at equal intervals for 3 minutes each time. Example 3: Initial charging amount / additional charging amount ratio = 0.15 / 0.
15 mol% (vs. total vinyl acetate), 2 additional charge
It was divided into 0 parts, and was charged at equal intervals for 3 minutes each time. Example 4: Initial charging amount / additional charging amount ratio = 0.12 / 0.
12 mol% (vs. total vinyl acetate) with additional charge of 3
It was divided into 0 parts, and was charged at equal intervals for 3 minutes each time.

Comparative Example 1 Polymerization was carried out in the same manner as in Example 1 except that the initial amounts of vinyl acetate and polyoxyethylene monoallyl ether were initially charged, followed by saponification and polyoxyalkylene group-containing polyvinyl alcohol as shown in Table 2. A system resin was obtained and the long-run moldability was evaluated in the same manner.

Comparative Example 2 Polymerization was carried out in the same manner as in Example 1 except that the total amount of polyoxyethylene monoallyl ether was initially charged, and saponification was performed to obtain a polyoxyalkylene group-containing polyvinyl alcohol resin as shown in Table 2. Then, the long-run moldability was evaluated in the same manner.

Comparative Example 3 Polymerization was carried out in the same manner as in Example 1 except that the initial amounts of polyoxyethylene monoallyl ether, vinyl acetate and azoisobutyronitrile were initially charged. An oxyalkylene group-containing polyvinyl alcohol-based resin was obtained, and long-run moldability was evaluated in the same manner.

Table 3 shows the evaluation results of Examples 1 to 4 and Comparative Examples 1 to 3.

[Table 1] Oxyalkylene group-containing monomer * Initial charge of each monomer / Type of vinyl ester monomer at the time of charge Drop charge (weight ratio) Monomer ratio PO monomer Binyl monomer (molar ratio) Example 1 POEMA (n = 10) / Vinyl acetate 40/60 40/60 2.5 / 100〃 2 POEMA (n = 10) / Vinyl acetate 40/60 40/60 2.5 / 100〃 3 POEMA (n = 10) / Vinyl acetate 40 / 60 40/60 2.5 / 100 〃 4 POEMA (n = 10) / vinyl acetate 30/70 30/70 2.5 / 100 * The types of oxyalkylene group-containing monomer are as follows, and the average of the group is shown in (). Indicates the chain length. PO monomer; oxyalkylene group-containing monomer POEMA; polyoxyethylene monoallyl ether

[0058] * 1: Measured by ¹ H-NMR

[0059]

[0060]

EFFECTS OF THE INVENTION The oxyalkylene group-containing polyvinyl alcohol-based resin which is the melt-molding resin of the present invention is obtained by a specific polymerization formulation, and therefore has excellent long-run moldability, and is used for packaging solid drugs such as detergents and agricultural chemicals. It is useful for pet related applications such as manure disposal bags, disposable diapers and sanitary items that can be discarded in water, and molding applications such as cores.

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Claims (6)

[Claims] 1. A saponification of an oxyalkylene group-containing vinyl ester copolymer obtained by copolymerizing an oxyalkylene group-containing monomer, a vinyl ester monomer and a polymerization catalyst into a polymerization system by continuously dropping or multi-dividing them. A resin for melt molding, comprising the polyvinyl alcohol resin containing an oxyalkylene group. 2. The amount of the oxyalkylene group-containing monomer and the amount of the vinyl ester monomer, which are continuously dropped or multi-divided, are 30 to 99% by weight based on the total amount of the respective monomers charged. Item 1
The melt molding resin described. 3. The oxyalkylene group-containing monomer / vinyl ester monomer molar ratio in continuous dropping or multi-division charging is 0.1 / 100 to 10/100, wherein the molar ratio is 0.1 / 100 to 10/100. Resin for melt molding. 4. The melt-molding resin according to claim 1, wherein the amount of the polymerization catalyst to be continuously dropped or multi-divided is 10 to 99% by weight of the total amount of the polymerization catalyst. . 5. The melt-molding resin according to claim 1, wherein the oxyalkylene group-containing vinyl ester copolymer is obtained by copolymerization in a batch system. 6. The melt molding resin according to claim 1, wherein the saponification degree is 80 mol% or more.