JPH03177431A - Molded article of moisture-shrinkable resin - Google Patents

Abstract

PURPOSE:To provide the subject composition for packaging material, etc., composed of graft copolymer of a thermoplastic resin and a polysaccharide originated from cellulose, vegetable gum, algae, etc., stable over a long period without lowering the film-strength such as tensile strength even after shrinkage with moisture and applicable even to a hot object. CONSTITUTION:The objective composition shrinkable by moisture absorption from air in a hot atmosphere at <=50 deg.C and a relative humidity of >=75% can be produced by the graft-copolymerization of (A) a polysaccharide (e.g. sodium alginate) comprising animal polysaccharide, microbial polysaccharide or vegetable mucin of cellulose, vegetable gum, algae or heteroglycan origin and (B) a thermoplastic resin (e.g. acrylic ester elastomer) at a weight ratio of preferably (85:15) to (15:85).

Description

[Detailed description of the invention] [Industrial application fields] The present invention relates to moisture-shrinkable resin molded articles.

[Prior Art] Conventionally, heat-shrinkable films and the like have been known as shrinkable resin molded products. Heat-shrinkable films include polyvinyl chloride film, polyvinylidene chloride film, polyethylene film, polypropylene film, polyamide film, etc., and are used for packaging foods such as fruits and vegetables, raw meat, and processed foods, as well as miscellaneous goods and precision parts. It is used in a wide range of applications, including packaging and virgin packaging for aerosol products and record jackets.

However, because heat-shrinkable films cannot be shrunk at low temperatures, they cannot be used for packaging foods, miscellaneous goods, precision parts, etc. that change in quality when heated. In order to solve this problem, we have recently developed a film that shrinks around room temperature when exposed to a high humidity atmosphere (US Pat. No. 4839).
No. 450) has been proposed.

[Problems to be Solved by the Invention] However, this film, which shrinks around room temperature when exposed to a high humidity atmosphere, is a film made of a stretched graft copolymer of a thermoplastic resin and starch (hereinafter referred to as a starch-based film). (abbreviated), and has problems such as a significant decrease in tensile strength after absorbing moisture and shrinking, and severe aging.

[Means for Solving the Problems] The present inventors have conducted intensive studies on shrinkable resin molded products that are stable for a long period of time and have little decrease in tensile strength even after absorbing moisture and shrinking at around room temperature. As a result, the present invention has been developed. reached. That is, the present invention provides polysaccharides selected from the group consisting of cellulose polysaccharides, plant rubber polysaccharides, seaweed polysaccharides, heteroglycan plant mucilage polysaccharides, animal polysaccharides, and microbial polysaccharides. This is a moisture-shrinkable resin molded product made of a graft copolymer of a thermoplastic resin, which is stretched, and is characterized by shrinking due to moisture.

In the present invention, the polysaccharides selected from the group consisting of cellulose polysaccharides, plant rubber polysaccharides, seaweed polysaccharides, heteroglycan plant mucilage polysaccharides, animal polysaccharides, and microbial polysaccharides include is not limited to natural polysaccharides, but also includes modified versions thereof; examples of cellulosic polysaccharides include methylcellulose, ethylcellulose, carboquine methylcellulose, hydroxyethylcellulose,
Hydroxypropyl cellulose, hydroxypropyl methyl cellulose, cellulose acetate, cellulose nitrate, etc. Plant gum polysaccharides include gum arabic, gum galati, gum karaya, gum tragacanth, etc.
Seaweed-based polysaccharides include agar, carrageenan, alginic acid, sodium alginate, and laminaran; heteroglycan plant mucilage-based polysaccharides include pectin, locust bean gum, guar gum, tamarind, galactomannan, and glucomannan; animal-based polysaccharides As for chitin,
Chitosan, hyaluronic acid, chondroitin, fundroitin sulfate, etc. Microbial polysaccharides (excluding starch-like polysaccharides) include xanthan gum, pullulan, curdlan, etc.; or hydrolysates, oxides, alkyl etherified products, aryls of these polysaccharides Examples include etherified products, oxyalkylated products, carboxymethylated products, aminoethyl etherified products, and organic acid esterified products.

Among these, preferred are cellulose polysaccharides,
Sodium alginate, xanthan gum, guar gum, locust bean gum and carrageenan.

In the present invention, thermoplastic resins include, for example, elastomers [thermoplastic elastomers (acrylic ester elastomers, ethylene-acrylic ester elastomers, vinyl chloride elastomers, polyolefin elastomers, polystyrene-polybutadiene copolymer thermoplastic elastomers, ethylene-vinyl acetate Elastomer Chlorinated polyethylene elastomer Polyester elastomer Polyamide elastomer), natural rubber and its derivatives (natural rubber, ebonite, chlorinated rubber, hydrochloric acid rubber, cyclized rubber, etc.), diene rubber (butadiene rubber, nitrile rubber, inblene rubber) , chloroprene rubber, etc.), olefin rubber (inbutylene rubber, isobutylene-diene rubber, ethylene-propylene rubber, chlorosulfonated polyethylene, etc.), polysulfide rubber, urethane rubber (polyester-isocyanate composite, polyether-isocyanate condensate, etc.), organosilicon compound rubber (silicone rubber)
, fluorine-containing compound rubber, etc., polyolefin tea plant I
ll [Polyethylene, polypropylene, ethylene-α
-Olefin copolymer, fluoropylene-α-olefin copolymer, poly-4-methylpentene, polybutene, etc.]
, styrenic resin [polystyrene, ASSiI2ABS
Gt resin, AAS resin, AES resin, AC8 resin,
MBS resin, styrene-butadiene resin, HIPS, etc., polymethyl methacrylate, vinyl chloride resin [polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, vinyl chloride-acrylic acid ester copolymer, vinyl chloride-methacrylic acid ester] Copolymers, etc., polyvinylidene chloride, polyvinyl acetate, ethylene-vinyl acetate copolymer,
Ionomer Boriacetal, Polyamide [Nylon 6, Nylon 66, Nylon 610, Nylon I L
Nylon 12, etc., polycarbonate, aromatic polyethers such as polyphenylene ether, polyethylene terephthalate, polybutylene terephthalate, polyarylate, polysulfone, polyether sulfone,
polyimide, polyamide toimide,
Examples include polyphenylene sulfide.

The above thermoplastic resins may be used alone or in combination of two or more. Among these, the preferred one is
Among the elastomers, particularly preferred are acrylic ester elastomers.

In the present invention, polysaccharides selected from the group consisting of cellulose polysaccharides, plant rubber polysaccharides, seaweed polysaccharides, plant mucilage polysaccharides of heteroglycans, animal polysaccharides, and microbial polysaccharides and heat When obtaining a graft copolymer of a plastic resin, a group consisting of cellulose polysaccharides, plant rubber polysaccharides, seaweed polysaccharides, plant mucilage polysaccharides of heteroglycans, animal polysaccharides, and microbial polysaccharides is used. The weight ratio of the selected polysaccharide and thermoplastic resin can vary depending on the required shrinkage performance, etc., but is usually 95:5 to 5.
:95, preferably 85:15 to I5285.

A graft of a thermoplastic resin and a polysaccharide selected from the group consisting of cellulose polysaccharides, plant rubber polysaccharides, seaweed polysaccharides, heteroglycan plant mucilage polysaccharides, animal polysaccharides, and microbial polysaccharides. The copolymer can be obtained by graft copolymerizing the above-mentioned polysaccharide with 7-mer, which becomes a thermoplastic resin after polymerization, or by performing a polymer reaction after graft copolymerization to impart thermoplasticity. Can be mentioned.

The monomer that becomes the thermoplastic resin after polymerization is not particularly limited as long as it forms the structure described in the section of the thermoplastic resin after polymerization.

The graft copolymerization method may be a conventionally known method, such as a method of graft copolymerization by irradiation with radiation, electron beams, ultraviolet rays, etc., cerium salt, inorganic peroxide [hydrogen peroxide, ammonium persulfate, persulfate] potassium, sodium persulfate, etc.], organic peroxides [benzoyl peroxide,
di-t-butyl peroxide, cumene hydroperoxide, succinic acid peroxide, di(2-ethoxyethyl) peroxydicarbonate, redox catalysts [alkali metal sulfites or bisulfites, ammonium sulfite, bisulfite] Azo compounds [azobisisobutyronitrile, azobiscyanovaleric acid, 2.2 '-azobis(2-amidinopropane) hydrochloride, etc.], and a method of graft copolymerization using two or more of these radical polymerization catalysts.

When the graft copolymer contains an acid group or a base, it can be neutralized if necessary. For example, when the polymer contains acid groups, an alkali metal compound can be added to form an alkali metal salt. This degree of neutralization is not particularly limited and can be varied.

In the present invention, examples of the graft copolymer include carboxymethylcellulose-methyl acrylate graft copolymer, xanthan gum-methyl acrylate graft copolymer, and sodium alginate-methyl acrylate graft copolymer.

In the present invention, polysaccharides selected from the group consisting of cellulose polysaccharides, plant rubber polysaccharides, seaweed polysaccharides, plant mucilage polysaccharides of heteroglycans, animal polysaccharides, and microbial polysaccharides and heat The plastic resin does not need to be entirely a graft copolymer, and a portion of each of these polysaccharides and resins may be contained as a homopolymer. In this case, polysaccharides selected from the group consisting of cellulose polysaccharides, plant rubber polysaccharides, seaweed polysaccharides, heteroglycan plant mucilage polysaccharides, animal polysaccharides, and microbial polysaccharides and thermoplastic The content of the graft copolymer in the resin is usually 20% or more, preferably 35% or more.

To obtain the moisture-shrinkable resin molded product of the present invention, for example, when obtaining a film-like molded product, the graft copolymer of the present invention may be stretch-molded by an extrusion stretch molding method, an inflation method, a calendar method, etc. It will be done. Another example is a method in which an unstretched film is obtained by a casting method or the like and then stretch-molded.

For example, when obtaining the film-like moisture-shrinkable resin molded product of the present invention by the inflation method, first, the graft copolymer of the present invention is heated using an extruder, kneaded, extruded into a tube shape, and solidified by cooling. to obtain an unstretched sheet.

Conditions such as the kneading temperature, the number of revolutions of the screw, and the thickness of the tubular sheet vary depending on the composition of the graft copolymer, the required performance of the film, etc., and are not particularly limited. During kneading, water, alcohol, a plasticizer such as urea, etc. can be added to the graft copolymer, if necessary. There is no particular restriction on the amount added. The obtained unstretched tubular sheet is then fed to a tubular stretching device and expanded and stretched in a temperature range where effective orientation occurs to effect simultaneous biaxial orientation. The stretching ratios do not have to be the same in length and width. The film taken out from the stretching device is re-dried as necessary.
Natural shrinkage of the film can be suppressed. Alternatively, an unstretched tubular sheet extruded from a tubular extrusion die may be expanded and stretched as it is to form a film all at once.

When obtaining a film-like moisture-shrinkable resin molded product of the present invention by a method of obtaining an unstretched sheet by a casting method or the like and then stretching it, first, the graft copolymer of the present invention is dissolved in a solvent, and the graft copolymer of the present invention is dissolved in a solvent. The solution is cast into a flat plate, dried with a drier or the like, and then separated by Q11 to obtain an unstretched sheet. The type of solvent, the concentration of the dissolving solution, the thickness of the sheet, etc. vary depending on the composition of the graft copolymer, the required performance of the film, etc., and are not particularly limited. When dissolving the graft copolymer in a solvent, a plasticizer such as alcohol can be added to the solvent as necessary. There is no particular restriction on the amount added. Next, the obtained unstretched sheet is heated to a temperature at which stretching is possible, stretched in the longitudinal direction and in the lateral direction, and then cooled. When using water, alcohol, etc. as a plasticizer during stretching, add it to the unstretched sheet when obtaining it, or soak the unstretched sheet in sample water, soak it in an alcohol solution, or expose it to its vapor. Methods such as these are taken.

The stretched film can be re-dried as necessary to suppress natural shrinkage of the film.

As extenders and additives for the moisture-shrinkable resin molded product of the present invention, plasticizers, fillers, foaming agents, mold release agents, lubricants, antiblocking agents, surfactants, easily decomposable additives, antistatic agents,
Pigments, dyes, colorants, fragrances, fillers, organic substances (pulp powder, polysaccharides, etc.), inorganic substances (silica, zeolite, activated carbon, far-infrared emitting ceramics, etc.), freshness-preserving agents,
Mixed with water-absorbing resin, desiccant, anti-fogging agent, deodorizing agent, aromatic agent, oxygen scavenger, ethylene adsorbent, medicinal ingredient, antibacterial agent, anti-mold agent, heat stabilizer, antioxidant, ultraviolet absorber, etc. It can be used as These can be mixed in various ways, such as mixing when obtaining a graft copolymer, mixing when obtaining a moisture-shrinkable resin molding from a graft copolymer, and mixing with a moisture-shrinkable resin molding. .

There is no particular restriction on the shape of the moisture-shrinkable resin molded product of the present invention, and it can be molded into any shape such as film, sheet, tape, net, foam, fiber, rod, etc. Preferably it is in the form of a film.

When the moisture-shrinkable resin molded product of the present invention is used in the form of a film, it can be laminated with another film by a method such as an extrusion B-laminate method or a dry lamination method.

For example, when obtaining a multilayer film by the Extru-Silon lamination method, there is a method in which laminated unstretched sheets are coextruded from a lamination die using a plurality of extruders and then stretched using a multilayer circular die or the like. Alternatively, when obtaining a multilayer film using the dry lamination method, an organic solvent adhesive such as urethane adhesive is applied onto the film-like moisture-shrinkable resin molding of the present invention, the solvent is removed by drying, and then other adhesives are applied. There is a method of laminating films using heat and pressure bonding. In addition, there is a method of thermocompression-bonding the film-like moisture-shrinkable resin molding of the present invention and another film using moisture, and a method of applying a solution containing other film components onto the film-like moisture-shrinkable resin molding of the present invention. There are methods such as applying and drying, but the method is not limited to these.

[Example] The present invention will be further explained below with reference to Examples, but the present invention is not limited thereto. Parts in the examples are parts by weight.

In addition, the shrinkage rate and bowing strength at each relative humidity in the examples were measured by the following operations.

1. Shrinkage rate at each relative humidity Each test film was left at room temperature under each relative humidity for 24 hours, and the longitudinal direction (MD) and transverse direction (TD) before and after shrinkage were measured.
The shrinkage rate was calculated from the ratio of each length.

2. Tensile Strength For each test film, the tensile strength of the film before shrinkage was measured using an Instron testing machine at a speed of 50 mm/min in the vertical axis direction. After these films were allowed to stand at room temperature and relative humidity of 90% for 24 hours, the tensile strength of the shrunk films was similarly measured. After storing this shrunken film for one month, the tensile strength was measured in the same manner.

Example 1 100 parts of carboxymethylcellulose and 4000ff of water
In addition to i, stir at room temperature under nitrogen atmosphere to completely dissolve, then add 150 parts of methyl acrylate, 8 parts of cerium ammonium nitrate, and 60 parts of IN nitric acid, and mix at 35-40°C.
The mixture was stirred for 3 and a half hours to polymerize. Next, the obtained product was added to excess methanol to precipitate it, then dried and pulverized to obtain a graft copolymer. This graft copolymer was mixed in a kneading extruder with an annular die at a resin temperature of 120 to 14
After melt-extruding at 0°C, the annular goo was maintained at 140°C. The longitudinal direction (MD)/transverse direction (TD) = 4.1/
Inflation stretching was performed at a stretching ratio of 4.5. Thickness of the obtained film-like moisture-shrinkable resin molded product of the present invention: 5
It was 5 μm. The performance measurement results of this product are also listed in Table 1.

Example 2 150 parts of sodium alginate was added to 3200 parts of water,
After stirring and dissolving at room temperature under nitrogen atmosphere, 300 parts of methyl acrylate, 3 parts of cerium ammonium nitrate, 6
50 parts of N nitric acid was added, and the mixture was stirred at 40 to 45° C. for 5 hours to polymerize. Next, the obtained product was filtered, washed with methanol, dried, and ground to obtain a graft copolymer. A small amount of water was added as a plasticizer to this graft copolymer, and the mixture was stirred to make it homogeneous. This is put into a hopper and put into a kneading extruder with an annular die at a resin temperature of 80 to 10.
After melt extrusion at 0°C, the annular die kept at 100°C longitudinal direction (MD)/horizontal direction (TD) = 3.8/4
．． Inflation stretching was carried out at a stretching ratio of 0. The obtained film-like moisture-shrinkable resin molded product of the present invention has a thickness of 65
It was μm. The performance measurement results of this product are also listed in Table 1.

Example 3 100 parts of powdered xanthan gum was added to 6000 parts of water, stirred and dissolved at 60°C under a nitrogen atmosphere, and then 200 parts of methyl acrylate, 2 parts of cerium ammonium sulfate,
50 parts of IN sulfuric acid was added, and the mixture was stirred at 70 to 75°C for 3 hours to polymerize. Next, the obtained product was added to excess methanol to precipitate it, then dried and pulverized to obtain a graft copolymer. A small amount of water was added as a plasticizer to this graft copolymer, and the mixture was stirred to make it homogeneous. This is introduced from a hopper, melted and extruded in a kneading extruder with an annular die at a resin temperature of 70 to 95°C, and then transferred from an annular goo kept at 95°C in the longitudinal direction (MD)/horizontal direction (TD). =
Inflation stretching was performed at a stretching ratio of 4.2/4.3. The thickness of the obtained film-like moisture-shrinkable resin molded product of the present invention was 50 μm. The performance measurement results of this product are also listed in Table 1.

Example 4 In the same manner as in Example 3, except that guar gum was used instead of powdered xanthan gum, the thickness was 60 μm.
A film-like moisture-shrinkable resin molded product of the present invention of m was obtained. The performance measurement results of this product are also listed in Table 1.

Example 5 In Example 3, the thickness was 45 μm in the same manner as in Example 3 except that chitosan was used instead of powdered xanthan gum.
A film-like moisture-shrinkable resin molded product of the present invention was obtained.

The performance measurement results of this product are also listed in Table 1.

Example 6 A product with a thickness of 65 mm was prepared in the same manner as in Example 3 except that gum arabic was used instead of powdered xanthan gum.
A film-like moisture-shrinkable resin molded product of the present invention having a diameter of μm was obtained. The performance measurement results of this product are also listed in Table 1.

Comparative Example 1 150 parts of cationic starch was dispersed in 3000 parts of water,
The temperature was raised to 35°C while stirring under a nitrogen atmosphere.

After being kept at 95°C for 30 minutes, it was cooled to 40°C. To this were added 225 parts of methyl acrylate, 5 parts of cerium ammonium nitrate, and 45 parts of IN nitric acid, and
The mixture was stirred for an hour to allow polymerization. Next, the obtained product was neutralized to pH 7 with an aqueous sodium hydroxide solution, added to excess methanol to precipitate it, and then dried and pulverized to obtain a starch-based graft copolymer. A small amount of water and urea are added as plasticizers to this starch-based graft copolymer,
Stir to make it homogeneous. This was introduced from a hopper, melted and extruded in a kneading extruder with an annular die at a resin temperature of 70 to 90°C, and then passed through an annular die maintained at 95°C in the longitudinal direction (MD)/horizontal direction (TD) = 4. Inflation stretching was carried out at a stretching ratio of .0/4.2. The thickness of the starch film obtained was 55 μm. The performance measurement results of this product are also listed in Table 1.

Comparative Example 2 Table 1 also shows the performance measurement results of a commercially available polyethylene heat-shrinkable film ("Oaklap PE Shrink", manufactured by Daikin Kogyo Co., Ltd.).

Table 1 Performance measurement results [Effects of the invention] By using the moisture-shrinkable resin molded product of the present invention,
It has the following effects.

(1) Stable for a long time even after absorbing moisture and shrinking.

Conventional starch-based films contain pregelatinized starch in their film constituents, so if they absorb water and are left to shrink, a so-called aging phenomenon occurs in which film strength such as tensile strength is significantly reduced. When the moisture-shrinkable resin molded product of the present invention is used in the form of a film, it does not contain starch in its constituent components, so even if it is stored for a long time after absorbing moisture and shrinking, the film strength such as tensile strength will decrease. decrease is small.

(2) There is little decrease in tensile strength immediately after absorbing moisture and shrinking.

Conventional starch-based films contain pregelatinized starch in their film constituents, so although the film strength in the dry state before shrinkage is good, once it absorbs moisture and shrinks, the film strength, especially the tensile strength, decreases significantly. descend. When the water-shrinkable resin molded product of the present invention is used in the form of a film, it does not contain starch in its constituent components, so after absorbing water and shrinking, there is no significant decrease in tensile strength as seen in starch-based films. do not have.

(3) It can also be applied to heat-sensitive materials that cannot be used with heat-shrinkable films or heat-shrinkable cloths.

Conventional heat-shrinkable films and heat-shrinkable cloths cannot be used for materials that change in quality when heated.

When the moisture-shrinkable resin molded product of the present invention is used in the form of a film or cloth, it can be shrunk even at low temperatures by absorbing moisture. In particular, even at temperatures below 50″C,
It can shrink simply by absorbing moisture in the air in a high humidity atmosphere with a relative humidity of 75% or more. For this reason,
Suitable for packaging items that are sensitive to heat.

Due to the above-mentioned effects, the moisture-shrinkable resin molded product of the present invention can be used for packaging materials (fruits and vegetables, processed foods, raw meat and other foods, miscellaneous goods, glass products, precision parts, scientific instruments, etc.), moisture detection materials (humidity sensors, etc.) It can be applied to equipment such as moisture detectors, leak detectors, etc.), agricultural materials, medical fields, diaper gears, and energy conversion devices.

Claims (1)

[Scope of Claims] 1. Selected from the group consisting of cellulose polysaccharides, plant rubber polysaccharides, seaweed polysaccharides, heteroglycan plant mucilage polysaccharides, animal polysaccharides, and microbial polysaccharides. A water-shrinkable resin molded product made of a graft copolymer of a polysaccharide and a thermoplastic resin, which is stretched and shrinks when exposed to water. 2. The molded article according to claim 1, which shrinks by absorbing moisture in the air in a high humidity atmosphere of 75% or more relative humidity at a temperature of 50° C. or less. 3. The molded article according to claim 1 or 2, wherein the thermoplastic resin is an elastomer. 4. The molded article according to any one of claims 1 to 3, wherein the moisture-shrinkable resin molded article has a film-like shape.