JPH10296820A - Manufacture of water soluble resin molded product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make industrial production of a water soluble resin molded product excellent by solving problems such as texture roughness, mucus, etc., in molding having excellent water solubility by a method wherein a shear speed and a resin temperature and specified in extrusion molding of a resin composition composed of starch, polyvinyl alcohol resin, and plasticizer. SOLUTION: A resin composition to be used is composed of starch, polyvinyl alcohol resin, and plasticizer, and as the starch, corn starch, potato starch, sweet potato starch, etc., are sued. As the polyvinyl alcohol resin, not only a partial saponified product or a complete saponified product of polyvinyl acetate, but also a monomer or the like capable of being copolymerized with vinyl ester are used. Further, as the plasticizer, polyhydric alcohols of ethylene glycol, glycerin, etc., are preferably sued. A shear speed in discharging from a die is set at 100 sec<-1> or higher. As a resin temperature in discharging in melt molding, it is so set as not to exceed 170 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a water-soluble resin molded product comprising starch (A), polyvinyl alcohol resin (B) and plasticizer (C).

[0002]

2. Description of the Related Art Conventionally, blended resin compositions of starch and polyvinyl alcohol resin have been known, and these resin compositions have been molded into various shapes and put to practical use. For example, in Japanese Patent Publication No. 7-5788, starch having a water content of 5 to 40% by weight is added at 105 to 240 ° C under a pressure of 15 to 240%.
A composition comprising a modified starch melted at 0 × 10 ⁵ N / m ² , a polyvinyl alcohol-based resin, and a specific thermoplastic polymer is disclosed. In Japanese Patent Publication No. 7-501090, polyvinyl alcohol is preliminarily plasticized. , A method for producing plasticized polyvinyl alcohol and mixing the same with starch is disclosed in JP-A-6-248150.
Disclosed are melt-moldable polyvinyl alcohol compositions containing 5% by weight of a plasticizer and compositions containing 5 to 95% by weight of a thermoplastic modified starch.

[0003]

[Problem to be Solved] However, Japanese Patent Publication No. 7-5788 discloses a technique disclosed in Japanese Patent Publication No. 7-501090.
JP-A-6-248150 or JP-A-6-248150 has problems in molding such as rough skin and eye grease during melt molding, is excellent in water solubility, and has a problem in forming such as rough skin and melt grease during melt molding. It is an object of the present invention to solve the problems and provide a technology that enables industrial productivity.

[0004]

Means for Solving the Problems As a result of intensive studies conducted by the present inventor to achieve the above object, the present inventors have obtained a resin composition comprising starch (A), polyvinyl alcohol resin (B) and plasticizer (C). In producing a molded product using a melt extruder, the shear rate of the resin composition when discharged from the die of the extruder is set to 100 sec ^-1 or more, and the temperature of the resin composition is set to 170 ° C. or less. The present inventors have found out that, when set, the molded product is water-soluble and solves molding problems such as rough skin and grease during molding, and completed the present invention.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described specifically. The resin composition used in the present invention comprises starch (A), polyvinyl alcohol resin (B), and plasticizer (C), and the starch (A) includes raw starch (corn starch, potato starch, sweet potato starch). , Wheat starch, kissava starch, sago starch, tapioca starch, sorghum starch,
Rice starch, bean starch, kudzu starch, bracken starch, lotus starch, sis starch, etc .; physically modified starch (α-starch, fractionated amylose, wet heat-treated starch, etc.); Amylose, etc.); chemically modified starch (acid-treated starch, hypochlorite oxidized starch, dialdehyde starch, etc.); chemically modified starch derivatives (esterified starch, etherified starch, cationized starch, cross-linked starch, etc.), etc. Can be

[0006] Among the chemically modified starch derivatives, the esterified starch includes acetate-starch, succinate-starch, nitrate-starch, phosphate-starch, urea-phosphate-starch, and xanthate-esterify. Starch, acetoacetic esterified starch and the like, as etherified starch, allyl etherified starch, methyl etherified starch, carboxymethyl etherified starch, hydroxyethyl etherified starch, hydroxypropyl etherified starch and the like, as cationized starch, Examples of crosslinked starch such as a reaction product of starch and 2-diethylaminoethyl chloride, a reaction product of starch and 2,3-epoxypropyltrimethylammonium chloride, formaldehyde crosslinked starch, epichlorohydrin crosslinked starch, phosphoric acid crosslinked starch, acrolein crosslinked starch Etc., and the like.

The polyvinyl alcohol resin (B)
Are usually produced by a known method, not only partially saponified or completely saponified polyvinyl acetate, but also monomers copolymerizable with vinyl esters, for example, ethylene, propylene, isobutylene, α-octene, α- Olefins such as dodecene and α-octadecene, acrylic acid,
Methacrylic acid, crotonic acid, maleic acid, maleic anhydride, unsaturated acids such as itaconic acid or salts or mono- or dialkyl esters thereof, acrylonitrile, nitriles such as methacrylonitrile, acrylamide,
Amides such as methacrylamide, ethylene sulfonic acid,
Allylsulfonic acid, olefinsulfonic acid such as methallylsulfonic acid or a salt thereof, alkyl vinyl ethers, N-acrylamidomethyltrimethylammonium chloride, allyltrimethylammonium chloride, dimethylallylvinylketone, N-vinylpyrrolidone, vinyl chloride, vinylidene chloride, Polyoxyalkylene (meth) allyl ethers such as polyoxyethylene (meth) allyl ether and polyoxypropylene (meth) allyl ether; polyoxyalkylene (meth) acrylates such as polyoxyethylene (meth) acrylate and polyoxypropylene (meth) acrylate A) acrylate, polyoxyethylene (meth) acrylamide, polyoxyalkylene (meth) acrylamide such as polyoxypropylene (meth) acrylamide, etc. De, polyoxyethylene (1
-(Meth) acrylamide-1,1-dimethylpropyl) ester, polyoxyethylene vinyl ether, polyoxypropylene vinyl ether, polyoxyethylene allylamine, polyoxypropylene allylamine,
Saponified copolymers with polyoxyethylene vinylamine, polyoxypropylene vinylamine and the like can be mentioned. Further, the polyvinyl alcohol resin (B) of the present invention may be a resin which has been "post-modified" such as oxyalkylene etherification, cyanoethylation, acetalization, urethanization, and acetoacetic esterification.

The preferred degree of saponification of the polyvinyl alcohol resin (B) of the present invention is 60 to 98 mol%. If the degree of saponification is less than 60 mol%, the solubility in water decreases, and conversely, 98 mol% If it exceeds, the solubility in water at low temperatures becomes poor, which is not preferred. The average degree of polymerization of polyvinyl alcohol is preferably 1800 or less, more preferably 1000 or less. If the average degree of polymerization exceeds 1800, the viscosity during melt-kneading becomes large, which is not preferable.

The plasticizer (C) is not particularly limited, but a polyhydric alcohol is preferably used. Examples of the alcohol include ethylene glycol, ethylene diglycol, polyethylene glycol, propylene glycol, propylene diglycol and polypropylene. Glycol, triethylene glycol, tripropylene glycol, trimethylene glycol, 1,2 propanediol, 1,3 propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5 -Hexanediol, 1,6-hexanediol, 1,5 pentanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, neopentyl glycol, hydrobenzoin,
Dihydric alcohols such as 1,2-cyclohexanediol, 1,4-cyclohexanediol and 1,4-cyclohexanedimethanol, trihydric alcohols such as glycerin, trimethylolpropane and trimethylolethane, and tetrahydric alcohols such as pentaerythritol; Examples thereof include mannitol, sorbitol, sorbitol acetate, sorbitol xylate, pentaerythritol acetate, and pentaerythritol xylate, and preferred are glycerin, sorbitol, and sorbitol acetate.

In the above resin composition, starch (A),
The mixing ratio of the polyvinyl alcohol-based resin (B) and the plasticizer (C) is not particularly limited, but the mixing ratio of the starch (A) and the polyvinyl alcohol-based resin (B) is 8 by weight.
The ratio is preferably from 0:20 to 5:95, particularly preferably from 70:30 to 10:90, and more preferably from 60:40 to 20:80. If the blending ratio of the starch (A) exceeds 80% by weight, the mechanical properties of the molded product become insufficient, while 5% by weight
If it is less than 5, there are problems such as stickiness and tackiness on the surface of the molded product, blocking between molded products, and poor contamination of the surface of the molded product. However, depending on the application, the amount may slightly deviate from the above mixing ratio.

The mixing ratio of the plasticizer (C) is preferably 5 to 30 parts by weight, more preferably 10 to 20 parts by weight, based on 100 parts by weight of the total of the starch (A) and the polyvinyl alcohol resin (B). It is. If the amount is less than 5 parts by weight, the plasticization and melt fluidity of the resin are insufficient, and the low-temperature processability (molding processability at 170 ° C. or lower) for suppressing the thermal decomposition of the starch (A) is insufficient, and 30 parts by weight. Exceeding the range is not preferable because the low-temperature processability is inferior to the compounding amount and the mechanical strength is insufficient.

In the present invention, it is preferable to mix the resin composition in which the polyvinyl alcohol resin (B) and the plasticizer (C) are mixed in advance and the starch (A) because the meltability of the resin composition is improved. The method will be described below. First, a polyvinyl alcohol-based resin (B) was added to a mixture of 60 to 100.
C., preferably 70 to 80.degree. C., charged into a mixing stirrer such as a kneader and stirred for 0.5 to 1 hour, based on the polyvinyl alcohol resin (B), 10 to 50% by weight, preferably 25 to 50% by weight. 40% by weight of plasticizer (C) is gradually added and mixed at 70 to 80 ° C for 2 to 3 hours to obtain a resin composition.
At this time, the plasticizer (C) may be added (dropped) in a lump or in a divided manner, but is preferably mixed and divided. Then, starch (A) is mixed with the resin composition (A),
A resin composition comprising (B) and (C) is obtained.

In the present invention, it is preferred that the resin composition comprising (A), (B) and (C) further contain a compatibility improver (D). This is particularly preferred because it has the effects of plasticizing the resin, stretching the molten resin, and imparting melt tension. As the compatibility improver (D), specifically, urea, N-ethylurea, N
Urea compounds such as -ethyl-N'-phenylurea and N-phenylurea can be mentioned, but urea is preferably used.

The mixing ratio of the compatibility improver (D) is 1% in total of starch (A) and polyvinyl alcohol resin (B).
The amount is preferably 1 to 20 parts by weight, more preferably 3 to 20 parts by weight.
To 10 parts by weight. If the amount is less than 1 part by weight, the effect of the present invention is not sufficiently exhibited, and if it exceeds 20 parts by weight, the mechanical strength is insufficient, which is not preferable. When the compatibility improver (D) is mixed with a starch (A) in a resin composition in which a polyvinyl alcohol-based resin (B) and a plasticizer (C) are previously mixed, the melting property of the resin composition becomes good. preferable.

In addition, if necessary, resin components other than those described above (ethylene copolymer and other polyolefins, hydrogenated styrene-butadiene rubber, polyurethane, polyamide, polyhydroxybutyrate, etc.), and natural polymers other than starch (polysaccharides) Polymers, cellulosic polymers, protein polymers, etc.), heat stabilizers, extenders, fillers, lubricants, coloring agents, flame retardants, water resistant agents, auto-oxidants, ultraviolet stabilizers,
Examples thereof include a cross-linking agent, an antibacterial agent, a herbicide, an antioxidant, and the like. Alkaline earths, alkali metal hydroxides, and mixtures thereof can also be added as a starch modifier.

Thus, the resin composition of the present invention is obtained. In the present invention, a molded product may be produced from the resin composition directly using a melt extruder. The composition is supplied to an extruder with a vent, melt-extruded into a strand, and pelletized with a pelletizer to obtain a compound composition pellet of the resin composition of the present invention.
Further, it is preferable to perform melt molding.

As the melting conditions used for obtaining the compound pellets, a single-screw extruder, a twin-screw extruder or the like is used as an extruder, and the screw diameter is 30 to 150.
mm, the screw rotation speed is 50 to 200 rpm,
The L / D is 30 to 40, and the die is 3 to 5 mm in diameter and has 2 to 30 nozzles. As the temperature condition of the extruder, the temperature of the cylinder is 100 to 170.
C., a die head temperature of 100 to 170.degree. C., and a die temperature of 100 to 130.degree.

The compound pellets can be obtained under the above-mentioned melting conditions. The greatest feature of the present invention is that the compound pellets (resin composition) obtained as described above are obtained by inflation molding, T-die molding, Injection molding method,
In producing a molded product by melt molding with a blow molding method or the like, the shear rate of the resin composition at the time of discharge from the die of the extruder is set to 100 sec ^-1 or more, and the temperature of the resin composition is 170 ° C. or less. The effect of the present invention can be obtained under such conditions.

More preferably, the shear rate is 120
８００800 sec ⁻¹ , more preferably 150 to 80 sec.
0 sec ^-1 . When the speed is less than 100 sec ^-1, the generation speed of the grease of the die lip is extremely fast, the grease adheres to the surface of the molded body, or bubbles enter the surface of the molded body,
It is not preferable because it has problems such as streaks.

As a specific method of controlling the shear rate, there is a method of adjusting the cross-sectional area of the slit and nozzle of the die and the extrusion rate (flow rate) of the resin.

The resin temperature at the time of discharge during melt molding is preferably 165 to 130 ° C., more preferably 165 to 14 ° C.
0 ° C. If the resin temperature exceeds 170 ° C., it becomes difficult to control the working conditions stably, or the starch (A) and the polyvinyl alcohol-based resin (B) undergo thermal decomposition, become colored, and become greasy to form a film. The surface is rough, or decomposition gas is generated, and bubbles or bubble marks enter the film, which is inappropriate.

As a method of controlling the resin temperature at the time of the discharge, specifically, the temperature of the heater is adjusted by using an extruder equipped with a heating type cylinder (barrel) capable of air cooling, water cooling or the like. And a method of appropriately adjusting the set temperature of the die in the range of 140 to 160 ° C., but a method of appropriately adjusting the set temperature of the die is preferable.

Thus, the water-soluble resin molded product of the present invention is obtained. Specifically, it is preferable that the film is formed into a film by an inflation molding method. The method will be described below.

As the die, a spiral round die or the like is used, and the diameter of the die is 40 to 400 mm. The die was attached and the various temperatures of the extruder were adjusted as described above. The compound pellets (resin composition) obtained above were first supplied to an extruder equipped with an annular die and melted at 140 to 165 ° C. It is kneaded, extruded into a tube shape from an annular die slit, and blown up.

At this time, the extrusion diameter of the extruder is 40 to 65 m.
m / L = 26-32, the diameter of the annular die can be 50-300 mm, and the gap of the die slit is practically in the range of 0.5-1.0 mm.

As the screw, a full flight type, a dub flight type, or a constant taper type is used, and the number of revolutions is adjusted by the discharge amount. Then, the extruded tube-shaped film is expanded to a predetermined diameter by gas pressure introduced from a gas blowing pipe inserted through the die, and then taken up at a constant speed by a nip roll, and the water-soluble film of the present invention is obtained. This is to obtain a resin molded product (film).

When a sheet is produced by the T-die molding method, a coat hanger type or a manifold type T-die (die width 40 to 1500 mm) is attached as a die, and the conditions of the extruder are adjusted. The compound pellets (resin composition) obtained above are adjusted in the same manner as in the case of the inflation die, supplied to an extruder equipped with a T-die, extruded into a sheet shape from a T-shaped die slit, and subjected to the present invention. This is to obtain a water-soluble resin molded product.

In the case of the injection molding method, a known molding machine such as a plunger type injection molding machine or a screw (in-line) type injection molding machine is used as the injection molding machine. ; 50 to 500 cc / sec
(Preferably 100 to 300 cc / sec), injection pressure; 100 to 1500 (preferably 300 to 1200 k)
g / cm ² ), nozzle temperature; 130 to 170 ° C. (preferably 130 to 160 ° C.), nozzle diameter: 3 to 5 mm (preferably 3.5 to 4 mm), cylinder temperature: 130 to 1
70 ° C (preferably 140 to 160 ° C), mold temperature; 1
The water-soluble resin molded product of the present invention can be obtained under molding conditions of 0 to 80 ° C (preferably 10 to 60 ° C).

In the case of blow molding, the parison to be extruded is placed in a mold of a hollow molding machine, and the parison is
To 170 ° C., preferably 120 to 160 ° C., blowing positive pressure air into the parison, hollow molding,
The bottle-shaped water-soluble resin molded article of the present invention is obtained.

In the case of vacuum forming, straight forming, drape forming, plug assist forming, air slip forming, snack back forming, plug assist forming, air slip forming, multi-mode forming, plug ring forming, contact heating forming, bottle-like deep forming Although any forming method such as draw forming and hollow body forming is adopted, a sheet is prepared using, for example, a T-die method, and the obtained sheet is heated to 60 to 100 ° C. by a vacuum pressure air forming machine. Thus, a water-soluble resin molded product of the present invention such as a cup or a tray is obtained.

The water-soluble resin molded product of the present invention thus obtained is used for packaging materials (films, sheets, bottles, cups, trays, can carriers, etc.); agricultural materials (agricultural films, binding tapes, plant roots, etc.). Film, seed tape, lawn foot pile, pesticide bottle, pesticide bag, powder fertilizer packaging bag), water-soluble consumer goods and consumer packaging film, laundry bag, napkin packaging bag, etc.), water-soluble (for non-woven fabric)
It can be used for various applications including fiber.

[0032]

The present invention will now be described more specifically with reference to examples. In the examples, “%” and “parts” are based on weight unless otherwise specified. Examples 1 to 4 (Production of compound pellets) 500 parts of a polyvinyl alcohol-based resin (polymerization degree: 600, saponification degree: 89 mol%) was charged into a kneader, and while stirring, 220 parts of glycerin was gradually added thereto at 80 ° C. for 2 hours. Mixed. Then, 570 parts of the mixture and corn starch (13.0% water),
40 parts of urea was charged into a Henschel mixer and mixed for 10 minutes. Next, a twin screw extruder with a vent (40 mm diameter)
And melt-extruded into strands, and pelletized with a pelletizer to obtain compound pellets.
The twin-screw extrusion conditions at this time were as follows.

Screw diameter 40 mm L / D 30 Screw rotation speed 130 rpm (rotation in the same direction) Vent Open vent Dies 5 nozzles with a diameter of 5 mm Temperature conditions Cylinder temperature (C ₁ , C ₂ , C ₃ , C ₄ , C ₅ ) Die head (H), Dies (D) C ₁ 100 ° C. C ₂ 150 ° C. C ₃ , C ₄ , C ₅ 150 ° C. H 140 ° C. D 130 ° C. Strand cooling A 10 ° C. cold air was blown by transporting the belt.

(Inflation Molding Method) The compound pellets obtained above are supplied to an inflation molding apparatus, and the purpose is to obtain a film having a thickness of 30 μm.
Molding was performed continuously for 2 hours. The conditions of the inflation molding method were as follows. Molding conditions Screw diameter 40 mm L / D 28 Screw rotation speed variable, discharge rate adjustment Screw shape Full flight type, constant taper type Compression ratio 2.5 die 60, 100 mm diameter spiral round die Die gap 0.5, 0.7 mm

Table 1 shows the inflation molding conditions. The measurement of the shear rate and the resin temperature at the time of discharge was obtained as follows.

The shear rate Fa (sec ⁻¹ ) is defined as follows: when the discharge amount of the melt discharged from the die lip is Q (g / sec), the die diameter is D (cm), and the die gap is G (cm). Fa = (6 × Q) / (π × D × G ² ).

Measurement of the resin temperature (discharge temperature) at the time of discharge is as follows.
A resin thermometer was installed at a joint connecting the cylinder and the round die of the extruder, and the temperature of the melt passing therethrough was measured.

The obtained molded product was evaluated as follows, and the results are shown in Table 2. The presence or absence of lip grease was observed. The surface condition of the molded product was evaluated as follows. ○ ・ ・ ・ Smooth surface, no skin roughness, no vertical stripes observed △ ・ ・ ・ Surface roughness and some vertical stripes observed × ・ ・ ・ Vertical stripes observed, and rough skin over the entire surface ×× ・..States in which vertical stripes are observed and the entire surface is rough and rough, and holes are partially observed

Example 5 In Example 1, the addition of 40 parts of urea was omitted, compound pellets were obtained in the same manner, inflation molding was performed, and the obtained molded product (film) was similarly evaluated. It was shown to.

Comparative Example 1 In Example 1, the addition of 570 parts of starch (A) was omitted, compound pellets were similarly obtained, and inflation molding was attempted. However, since the molten resin was sticky and had no melt tension, inflation was not performed. Molding (film formation) could not be performed.

Comparative Example 2 In Example 1, the polyvinyl alcohol resin (B)
Addition of 500 parts was omitted, and other components were blended to form compound pellets. However, the viscosity of the melt was large, there was no strand take-off property, and compound pellets could not be produced.

Comparative Example 3 In Example 1, the addition of 200 parts of glycerin (C) was omitted, and other components were blended to form a compound pellet. However, plasticization and melting of the polyvinyl alcohol resin (A) were performed. Compound pellets could not be produced.

Comparative Example 4 In Example 1, the temperature of the cylinder and the die was set to 170
The temperature at the time of discharge from the die of the extruder was set to 180 ° C., a molded product (film) was produced in the same manner as in Example 1, and evaluated in the same manner as in Example 1. Table 2
It was shown to.

Comparative Example 5 In Example 1, the screw speed of the extruder was controlled to reduce the discharge rate, the die slip gap was set to 1.0 mm, the shear rate was set to 76 sec ⁻¹ , and the molded product ( A film was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0045]

[Table 1] Diester discharge amount Discharge temperature Shear rate (mm) (mm) (kg / hr) (° C) (sec ^-1 ) Example 1 100 0.5 10 155 212 〃 2 100 0.7 15 153 162 ３ 360 0.5 15 165 531 ４ 4 60 0.5 20 165 708 〃 5 60 0.7 15 160 271 Comparative Example 4 60 0.7 15 180 530 ５ 5 100 0.7 7 150 76

[0046]

[Table 2]

Examples 6 to 8, Comparative Examples 6 and 7 (T-die molding method) Compound pellets (resin composition) obtained in the same manner as in Examples 1 to 4 were extruded by a single screw equipped with a T-die. The sheet was supplied to the apparatus, and molding was continuously performed for 6 hours with the aim of obtaining a sheet having a thickness of 500 μm. The conditions of the extruder and the die used were as follows. Molding conditions Screw diameter 40 mm L / D 28 Screw rotation speed variable, discharge rate adjustment Screw shape Full flight type, constant taper type Compression ratio 2.5 die Coat hanger type T-die Die width 450 mm

Table 3 shows the T-die molding conditions. In addition,
The measurement of the shear rate and the discharge temperature was obtained as follows.

The measurement of the resin temperature (discharge temperature) at the time of discharge is as follows.
A resin thermometer was installed at a joint connecting the cylinder of the extruder and the T-die, and the temperature of the melt passing therethrough was measured.

The shear rate Fa (sec ^-1 ) is defined as follows: when the discharge amount of the melt discharged from the die lip is Q (g / sec), the die width is W (cm), and the die gap is G (cm). Fa = (6 × Q) / (W × G ² ).

The obtained molded product was evaluated in the same manner as in Example 1, and the results are shown in Table 4.

[Table 3] Discharge amount Discharge temperature Discharge temperature Shear rate (mm) (kg / hr) (° C) (sec ^-1 ) Example 6 0.5 12 155 178 ７ 7 0.5 15 158 222 ８ 8 0.7 20 160 151 Comparative example 6 0.7 10 155 75 ７ 7 0.5 15 183 222

[0052]

[Table 4]

(Blow Molding Method) Examples 9 and 10, Comparative Examples 8 and 9 A compound pellet (resin composition) obtained in the same manner as in Examples 1 to 4 was prepared using a parison die having an outer diameter of 30 mm and an inner diameter of 26 mm, and a diameter of 60 mm. A bottle was molded using a bottle molding tester equipped with a 100 mm high wide-mouth bottle blow mold. Molding conditions Screw diameter 50mm L / D 28 Screw rotation speed variable, discharge rate adjustment Screw shape Full flight type Compression ratio 3.0

Table 5 shows the conditions of the blow molding method. The measurement of the shear rate and the discharge temperature was determined as follows.

The shear rate Fa (sec ⁻¹ ) is defined as follows: when the discharge amount of the melt discharged from the die lip is Q (g / sec), the die diameter is D (cm), and the die gap is G (cm). Fa = (6 × Q) / (π × D × G ² ).

Measurement of the resin temperature (discharge temperature) at the time of discharge is as follows.
A resin thermometer was installed at the joint between the extruder and the parison die, and the temperature of the melt passing therethrough was measured.

The obtained molded product was evaluated in the same manner as in Example 1, and the results are shown in Table 6.

[Table 5]

[0058]

[Table 6]

[0059]

According to the present invention, a resin composition comprising a starch (A), a polyvinyl alcohol resin (B) and a plasticizer (C) is used to produce a molded product using a melt extruder. Since the shear rate of the resin composition when discharged from the resin composition is set to 100 sec ^-1 or more and the temperature of the resin composition is set to 170 ° C. or less, there is no grease and the surface condition of the molded article is good. A resinous molded product can be obtained, and packaging materials (films, sheets, bottles, cups, trays, can carriers, etc.); agricultural materials (agricultural films, bundling tapes, root-wrapping films for plant trees, seed tapes, lawn retainers) Pile, pesticide bottle, pesticide bag, powder fertilizer packaging bag), water-soluble consumer goods and consumer packaging film, laundry bag, napkin packaging bag, etc.), water-soluble (for non-woven fabric) fiber, Can.

Claims (10)

[Claims] 1. A resin composition comprising a starch (A), a polyvinyl alcohol resin (B) and a plasticizer (C) is produced from a die of an extruder when a molded product is produced using a melt extruder. The shear rate of the resin composition at the time is 100 sec ^-1
A method for producing a water-soluble resin molded product, wherein the temperature is set to 170 ° C. or lower, and the temperature is set to 170 ° C. or lower. 2. The resin composition further comprises a compatibility improver (D).
The method for producing a water-soluble resin molded product according to claim 1, further comprising: 3. The method for producing a water-soluble resin molded product according to claim 2, wherein the compatibility improving agent (D) is a urea compound. 4. The resin composition according to claim 1, wherein the polyvinyl alcohol resin (B) and the plasticizer (C) are mixed in advance, and further the starch (A) is mixed. The method for producing a water-soluble resin molded article according to any one of the above. 5. The method for producing a water-soluble resin molded product according to claim 1, wherein the resin molded product discharged from the die is a water-soluble resin film. 6. The method for producing a water-soluble resin molded product according to claim 1, which is produced by an inflation molding method or a T-die molding method. 7. A sheet is produced by a T-die molding method, and then the sheet is vacuum molded.
A method for producing the water-soluble resin molded article according to the above. 8. The method for producing a water-soluble resin molded product according to claim 1, which is produced by an injection molding method or a blow molding method. 9. The method for producing a water-soluble resin molded product according to claim 1, wherein the water-soluble resin molded product is a water-soluble resin fiber. 10. The method for producing a water-soluble resin molded article according to claim 9, wherein the water-soluble resin fiber is a water-soluble resin fiber for a nonwoven fabric.