JPH06256533A - Production of polyvinyl alcohol-based resin molded product - Google Patents

Abstract

PURPOSE:To advantageously obtain the subject molded product good in long-run operability even on an industrial scale. by molding an oxyalkylene group-bearing polyvinyl alcohol (esp. blow molding or inflation molding) in a molten state. CONSTITUTION:Oxyalkylene group-bearing polyvinyl alcohol granules are brought into contact with a boron compound solution to make its content to 0.01-5wt.% in the boron compound and <=0.5wt.% volatiles contents of the granules, respectively, and then carrying out a molding of the granules in a molten state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a method for producing a molded article, which can be obtained by blow molding or inflation molding.

[0002]

2. Description of the Related Art Molded products of polyvinyl alcohol, especially molded products of oxyalkylene group-containing polyvinyl alcohol,
For example, the film is excellent in properties such as solvent resistance, aroma retention, transparency, oil resistance, antistatic property, oxygen barrier property, heat retention property, etc., as compared with molded products such as polyolefin and polyester, and also hydrophilicity, Since it has water solubility or water dispersibility, it is effectively used for packaging agricultural chemicals, oils and fats, solvents and the like.

Oxyalkylene group-containing polyvinyl alcohol is a known polymer, and for example, the following various foreign applications have been made. For example, US Patent No. 1971
No. 662, No. 2844570, No. 299
No. 0398 discloses oxyalkylene group-containing polyvinyl alcohol obtained by addition reaction of ethylene oxide with polyvinyl alcohol. US Patent No. 30
No. 3,384,1 and No. 4,369,281,
An oxyalkylene group-containing polyalkylene glycol obtained by saponifying a polymer obtained by graft-polymerizing vinyl acetate in the presence of polyalkylene glycol is shown. U.S. Pat. Nos. 4,618,648 and 4,675,360 show copolymers of vinyl alcohol and poly (alkyleneoxy) acrylates, which are injection-moldable and extrudable. It has also been shown that the resulting moldings have water solubility and flexibility.

Japanese Unexamined Patent Publication No. 59-1655408 discloses that
A modified polyvinyl alcohol obtained by saponifying a copolymer of an unsaturated monomer containing an oxyalkylene group and vinyl acetate is shown. Various types of applications are listed in the publication, and molded articles are also mentioned as an example of the applications. JP-A-3-203932 filed by the present applicant discloses a method of melt-molding an oxyalkylene group-containing vinyl alcohol copolymer under substantially anhydrous conditions. The publication describes that molding is performed substantially without using a plasticizer, and extrusion molding or injection molding can be used as a molding method.

[0005]

In the case of an oxyalkylene group-containing polyvinyl alcohol resin, in order to obtain a molded product by blow molding, it is necessary to increase the melt tension in order to avoid drawdown of the parison, and inflation molding is also necessary. Therefore, in order to obtain a molded product, it is necessary to increase the melt tension in order to form bubbles, but for that purpose, it is necessary to have a high degree of polymerization and a high viscosity. Generally, a high-viscosity resin is liable to generate gels, eye blemishes, etc., and has a low long-run property, making it difficult to carry out molding for a long time, which is extremely disadvantageous in molding on an industrial scale. Therefore, there is a demand for a method for producing an oxyalkylene group-containing polyvinyl alcohol-based molded product, which enables favorable blow molding and inflation molding even on an industrial scale.

[0006]

However, as a result of intensive studies by the present inventors in order to solve such a problem, the oxyalkylene group-containing polyvinyl alcohol particles were brought into contact with a boron compound solution to reduce the boron compound content to 0. 01-5
% By weight and volatile content below 0.5% by weight,
When the particles were melt-molded, they found that they met such an object and completed the invention. The present invention, the oxyalkylene group-containing polyvinyl alcohol is contacted with a boron compound solution, to improve the melt tension (melt tension) of the resin by containing a specific amount of the boron compound and volatile matter, blow molding even at a low degree of polymerization, Inflation molding was made possible. Hereinafter, the present invention will be described in detail.

The oxyalkylene group-containing polyvinyl alcohol used in the present invention is typically vinyl acetate and polyoxyalkylene (meth) such as polyoxyethylene (meth) allyl ether and polyoxypropylene (meth) allyl ether. Copolymerized with allyl ether,
It is then obtained by saponification. In this case, the copolymerization ratio of the polyoxyalkylene (meth) allyl ether is 0.1 to 20 mol%, particularly 0.1 to 5 mol%, and the polyoxyalkylene condensation degree in the polyoxyalkylene (meth) allyl ether is 1 ~ 300, especially 3-50,
The proportion of oxyalkylene units in the entire oxyalkylene group-containing polyvinyl alcohol is preferably 3 to 40% by weight. This indicates that there is an optimum range for the degree of localization-delocalization of oxyalkylene units and the length of oxyalkylene units in the copolymer.

In the oxyalkylene group-containing polyvinyl alcohol to be treated with the boron compound, the degree of saponification of vinyl acetate units is 60 to 100 mol%, preferably 80.
To 100 mol% and the average degree of polymerization is 100 to 150.
0, preferably 200 to 800 is suitable. Also, when performing blow molding or inflation molding,
The melt index at 210 ° C. and a load of 2160 g is 5 to 100 g / 10 minutes, preferably 5 to 50 g / 10.
Minutes are appropriate. When the melt index is less than 5 g / 10 minutes, the oxyalkylene group-containing polyvinyl alcohol has a large degree of polymerization and thus has a high melt viscosity. When a boron compound is added, the melt viscosity further increases and molding becomes difficult. If it exceeds 100 g / 10 min, the oxyalkylene group-containing polyvinyl alcohol has a low degree of polymerization, so that the molded product cannot have sufficient strength.

As the copolymerization component, components other than polyoxyalkylene (meth) allyl ether, such as α-olefin (ethylene, propylene, long-chain α-olefin, etc.), ethylenically unsaturated carboxylic acid monomer, (acrylate, Methacrylate, acrylonitrile, methacrylonitrile, vinyl chloride, vinyl ether, etc.) 30
You may contain if it is about mol% or less. As the polymerization method for obtaining the oxyalkylene group-containing polyvinyl alcohol, a solution polymerization method is usually adopted, and a suspension polymerization method, an emulsion polymerization method or the like can be adopted depending on the case. As the saponification reaction, an alkali saponification method, an acid saponification method or the like is adopted.

In addition to the above, polyvinyl alcohols containing oxyalkylene groups include vinyl acetate, polyoxyethylene (meth) acrylate, and polyoxypropylene (meth).
Acrylate, polyoxyethylene (meth) acrylamide, polyoxypropylene (meth) acrylamide,
Polyoxyethylene (1- (meth) acrylamide-
1,1-Dimethylpropyl) ester, polyoxyethylene vinyl ether, polyoxypropylene vinyl ether, polyoxyethylene amine, polyoxypropylene allylamine and other polyoxyalkylene allylamine, polyoxyethylene vinyl amine, polyoxypropylene vinylamine and other polyoxy It can also be obtained by copolymerizing alkylene vinyl amine or the like and then saponifying. The oxyalkylene group-containing polyvinyl alcohol can also be obtained by reacting alkylene oxide with polyvinyl alcohol, or by polymerizing vinyl acetate with polyoxyalkylene glycol and subsequent saponification.

As the method for producing a polyvinyl alcohol-based resin molded product in the present invention, polyvinyl alcohol particles containing an oxyalkylene group are brought into contact with a boron compound solution so that the boron compound content is 0.01 to 5% by weight and the volatile content is After the content is 0.5% by weight or less, the particles are melt-molded. Specifically, a boron compound is added to a solvent heated to 20 to 100 ° C., for example, water, alcohol or the like, and stirred to prepare a concentration of 0.05 to 5% by weight, and such a solution is added to an oxyalkylene group-containing polyvinyl alcohol. The particles are contacted and dried. The particles thus treated have a boron compound content of 0.01 to 5% by weight, preferably 0.1 to 5% by weight.
1.0% by weight, volatile content is 0.5% by weight or less, preferably 0.3% by weight or less. When the content of the boron compound is less than 0.01% by weight, the effect of increasing the melt tension is very small, and when it exceeds 5% by weight, the melt tension increases, but the amount of the boron compound added is large, so that gel and foreign matter are not generated. Occurs and the long-run property deteriorates.

If the volatile content exceeds 0.5% by weight, bubbles will be generated. In order to favorably perform blow molding or inflation molding, the melt index of the oxyalkylene group-containing polyvinyl alcohol treated with a boron compound at 210 ° C. and 2160 g is 0.1 to 4.9 g / 10 minutes, preferably 0.3. ~ 4.
A suitable value is 0 g / 10 minutes and a melt index of 0.
If it is less than 1 g / 10 minutes, the long-run property is not improved by adding boric acid, and if it exceeds 4.9 g / 10 minutes, blow molding and inflation molding are generally difficult. Examples of the boron compound in the above include boric acid or a salt thereof, borax and the like. Examples of the solvent in the above include water, alcohols such as methanol and ethanol, and methanol is particularly preferable.

The oxyalkylene group-containing polyvinyl alcohol resin particles thus obtained are melt-molded, for example, blow-molded or inflation-molded. At the time of melt molding, various additives such as a plasticizer, a lubricant, a filler, a colorant and a stabilizer can be blended. Further, other polymers may be blended within the range not impairing the gist of the present invention. Next, blow molding will be described. First, the oxyalkylene group-containing polyvinyl alcohol resin is supplied to an extruder, melt-kneaded, and extruded to obtain a parison. The extruder temperature at this time is preferably 170 to 220 ° C. Then, the parison is installed in a mold of a blow molding machine and adjusted to a temperature of 150 to 220 ° C., and a positive pressure fluid is blown into the parison for blow molding. The molded product after blowing is taken out from the mold after cooling and becomes a product.

Next, inflation molding will be described. The above-mentioned oxyalkylene group-containing polyvinyl alcohol-based resin is supplied to an extrusion molding machine equipped with a die slit called a ring die, a circular die, a round die, etc., melt-kneaded and extruded into a tubular shape, and air is introduced into the tubular resin. Blow in. The extruder temperature at this time is appropriately 170 to 220 ° C. Then, while cooling, flatten it with two plates called guide plates, stabilizers, etc., which are arranged in a palm-like shape several meters above, and continuously take it up with a pinch roll and wind it up.
Obtain a tubular film. The melt molding method in the present invention includes injection molding method, transfer molding method, co-extrusion molding, extrusion molding such as extrusion coating, etc., in addition to blow molding and inflation molding. The form of such a molded article is not particularly limited, and includes bottles, films, sheets, hoses, tubes, containers, bags,
Examples thereof include fibers and foams.

[0015]

[Operation] The present invention provides a molding method in which blow molding and inflation molding can be favorably carried out even on an industrial scale.

[0016]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to actual examples. Example 1 Polyoxyethylene monoallyl ether having an average degree of condensation of oxyethylene of 10 and vinyl acetate were copolymerized in methanol in the presence of azobisisobutyronitrile, and then residual monomers were expelled, followed by hydroxylation. A sodium solution of sodium was added for saponification. The copolymer was filtered off from the slurry produced by the saponification reaction, and washed with methanol of 5 times the apparent volume of polyvinyl alcohol powder three times. The melt index of the oxyalkylene group-containing polyvinyl alcohol at 210 ° C. and 2160 g (measurement use model name: MELT INDEXER,
20g / 10 for Toyo Seiki Seisakusho Co., Ltd.)
It was a minute. Then, it was brought into contact with a methanol solution containing 0.5% by weight of boric acid and dried to obtain oxyalkylene group-containing polyvinyl alcohol particles. The weight average degree of polymerization of this polymer was 360, the copolymerization ratio of polyoxyethylene monoallyl ether units was 1.5 mol%, and the ratio of oxyalkylene units in the whole polymer was 14.1.
% By weight, saponification degree of vinyl acetate component was 95 mol%, boric acid content was 0.2% by weight, methanol content was 0.3% by weight, and melt index at 210 ° C. and 2160 g was 3.8 g / 10 minutes. . The long-run property of this resin was evaluated by the following method. The results are summarized in Table 1.

(1) The polyvinyl alcohol containing an oxyalkylene group obtained above is fed to an extruder at a temperature of 210 ° C.
Was melt-kneaded, and a pipe having a structure of 0.7 mm in thickness and 230 mm in height was extruded, and one end of the pipe was made blind to form a parison. The temperature of the parison at this time was 200 ° C. Next, the parison was clamped with a mold, blown with compressed air, and blow-molded to form a 2.5-liter round bottle (thickness 1.0 mm). When performing such blow molding continuously for 12 hours, observe the presence or absence of occurrence of eye blemishes,
If so, the time was recorded. (2) The oxyalkylene group-containing polyvinyl alcohol obtained above was fed to an extruder equipped with a ring die to obtain a temperature of 2
Melt and knead at 10 ℃, discharge from ring die slit with slit diameter 100mm, slit clearance 1.5mm at temperature 210 ℃, blow cooling air to form a tubular film, flatten it with a stabilizer and take it out with a pinch roll. I wound up. The discharge rate of the resin was 7 kg / hr and the film take-up speed was 10 m / min. When performing such inflation molding continuously for 10 hours, five 50 cm × 50 cm films were sampled with time, foreign substances in the films were observed with a magnifying glass, the number was counted, and the average value was obtained.

Example 2 The following oxyalkylene group-containing polyvinyl alcohol particles were produced according to Example 1 and evaluated for long-run property. The results are summarized in Table 1. Weight average degree of polymerization: 300 Saponification degree of vinyl acetate component: 97 mol% Polyoxyethylene monoallyl ether (degree of condensation of oxyethylene 10) unit copolymerization ratio: 2.0 mol% Oxyalkylene in the whole polymer Unit ratio: 1
6.2% by weight Melt index of oxyalkylene group-containing polyvinyl alcohol-based resin before treatment: 50 g / 10 minutes Boric acid content: 0.4% by weight Methanol content: 0.2% by weight Oxygen after contact with boric acid solution Melt index of alkylene group-containing polyvinyl alcohol: 4.8 g / 10 minutes

Example 3 Oxyalkylene group-containing polyvinyl alcohol particles shown below were produced according to Example 1 and evaluated for long-run property. The results are summarized in Table 1. Weight average degree of polymerization: 410 Saponification degree of vinyl acetate component: 96 mol% Polyoxypropylene monoallyl ether (condensation degree of oxypropylene 10) unit copolymerization ratio: 2.5 mol% of oxyalkylene units in the entire polymer Ratio: 1
9.2 wt% Melt index of oxyalkylene group-containing polyvinyl alcohol-based resin before treatment: 10 g / 10 min Boric acid content: 0.3 wt% Methanol content: 0.4 wt% Oxygen after contact with boric acid solution Melt index of alkylene group-containing polyvinyl alcohol resin: 2.5 g / 1
0 minutes

Example 4 Oxyalkylene group-containing polyvinyl alcohol particles shown below were produced according to Example 1 and evaluated for long-run property. The results are summarized in Table 1. Weight average degree of polymerization: 430 Degree of saponification of vinyl acetate component: 92 mol% Copolymerization ratio of polyoxyethylene acrylamide monomer (condensation degree of oxyethylene 20) unit: 1.0 mol% Ratio of oxyalkylene units in the entire polymer : 1
6.9 wt% Melt index of oxyalkylene group-containing polyvinyl alcohol resin before treatment: 7 g / 10 min Boric acid content: 0.2 wt% Methanol content: 0.5 wt% Oxygen after contact with boric acid solution Melt index of alkylene group-containing polyvinyl alcohol-based resin: 1.8 g / 1
0 minutes

Example 5 Oxyalkylene group-containing polyvinyl alcohol particles shown below were produced according to Example 1 and evaluated for long-run property. The results are summarized in Table 1. Weight average degree of polymerization: 450 Saponification degree of vinyl acetate component: 98 mol% Polyoxypropylene methacrylamide monomer (oxypropylene condensation degree 10) unit copolymerization ratio: 3.0
Mol% Polymer-Ratio of oxyalkylene units in the whole polymer: 2
7.4 wt% Melt index of oxyalkylene group-containing polyvinyl alcohol resin before treatment: 5 g / 10 min Boric acid content: 0.1 wt% Methanol content: 0.1 wt% Oxygen after contact with boric acid solution Melt index of alkylene group-containing polyvinyl alcohol-based resin: 2.7 g / 1
0 minutes

Example 6 Oxyalkylene group-containing polyvinyl alcohol particles shown below were produced according to Example 1 and evaluated for long-run property. The results are summarized in Table 1. Weight average degree of polymerization: 410 Degree of saponification of vinyl acetate component: 96 mol% Polyoxyethylene vinyl ether monomer (degree of condensation of oxyethylene 8) unit copolymerization ratio: 2.5 mol% Ratio of oxyalkylene units in the entire polymer : 1
9.4 wt% Melt index of oxyalkylene group-containing polyvinyl alcohol-based resin before treatment: 10 g / 10 min Boric acid content: 0.5 wt% Methanol content: 0.2 wt% Oxygen after contact with boric acid solution Melt index of alkylene group-containing polyvinyl alcohol-based resin: 1.1 g / 1
0 minutes

Example 7 Oxyalkylene group-containing polyvinyl alcohol particles shown below were produced according to Example 1 and evaluated for long-run property. The results are summarized in Table 1. Weight average degree of polymerization: 450 Saponification degree of vinyl acetate component: 98 mol% Polyoxypropylene vinyl ether monomer (condensation degree of oxypropylene 13) unit copolymerization ratio: 3.0 mol% Ratio of oxyalkylene units in the entire polymer : 2
8.7% by weight Melt index of oxyalkylene group-containing polyvinyl alcohol-based resin before treatment: 5 g / 10 minutes Boric acid content: 0.8% by weight Methanol content: 0.1% by weight Oxygen after contact with boric acid solution Melt index of alkylene group-containing polyvinyl alcohol-based resin: 0.3 g / 1
0 minutes

Comparative Example 1 An experiment was carried out in the same manner as in Example 1 except that the boric acid content was 8% by weight. The results are summarized in Table 1. Comparative Example 2 An experiment was carried out in the same manner as in Example 1 except that the methanol content was changed to 3% by weight. The results are summarized in Table 1. Comparative Example 3 When an experiment was conducted in the same manner as in Example 1 except that boric acid was not added, blow molding and inflation molding could not be performed well.

[0025]

[Table 1]

[0026]

INDUSTRIAL APPLICABILITY The present invention makes blow molding and inflation molding advantageous on an industrial scale by bringing an oxyalkylene group-containing polyvinyl alcohol into contact with a boron compound solution to contain a specific amount of the boron compound and a volatile component. I was able to do it.

Claims (3)

[Claims] 1. Oxyalkylene group-containing polyvinyl alcohol particles are brought into contact with a boron compound solution, the boron compound content is 0.01 to 5% by weight, and the volatile content is 0.5.
A method for producing a polyvinyl alcohol-based resin molded product, which comprises melt-molding the particles after adjusting the content to be not more than 10% by weight. 2. The method according to claim 1, wherein the melt index of the treated particles is 0.1 to 4.9 g / 10 minutes. 3. The melt index is 5 to 100 g / 1.
The production method according to claim 1, wherein the oxyalkylene group-containing polyvinyl alcohol at 0 minutes is contacted with the boron compound.