JPH0592507A - Starch-based polymer laminated structure - Google Patents

Abstract

(57) [Summary] [Object] The present invention provides a starch-based polymer laminated structure having improved moldability. [Structure] A starch-based polymer laminated structure in which a layer of a composition comprising a starch-based polymer and a saponified ethylene-vinyl acetate copolymer is laminated with another substrate. [Effect] By adding EVOH to a starch-based polymer, its melt moldability is improved, so that a laminated structure can be easily produced, and it can be used in a wider range of applications by utilizing the barrier property and oil resistance of starch.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated structure comprising a starch polymer layer and another substrate.

[0002]

2. Description of the Related Art Starch polymer films have the characteristics of being inexpensive, having oil resistance, and being excellent in gas barrier properties.
It has the major drawback of being inferior in mechanical strength and water resistance. Therefore, in order to eliminate this drawback, it is conceivable to reinforce by using a laminated structure with another base film. However, in this case, the starch-based polymer is not thermoplastic and is difficult to be melt-molded. Therefore, in reality, the starch-based polymer has to be laminated on the substrate by the casting method.

[Problems to be Solved by the Invention]

However, the lamination of the starch-based polymer by such a casting method requires a plurality of steps such as casting and drying, so that the characteristics of the starch-based polymer are not impaired and the melt-molding can be easily carried out. There is a need for improvements such that laminated structures can be manufactured.

[0004]

The inventors of the present invention have conducted extensive studies in order to solve the above problems, and as a result, have found that a starch-based polymer and a saponified ethylene-vinyl acetate copolymer (hereinafter abbreviated as EVOH). The present invention has been completed, and it was found that the use of the composition consisting of (1) and (2) can easily form a laminated structure with another substrate without impairing the properties of the starch-based polymer.

That is, the present invention is "a starch-based polymer laminated structure in which a layer of a composition comprising a starch-based polymer and a saponified ethylene-vinyl acetate copolymer is laminated with another substrate." Is. Attempts have been made to mix various thermoplastic resins with starch-based polymers and perform melt molding, but in order to maintain the oil resistance and gas barrier properties of starch-based polymers, the amount of thermoplastic resin blended Inevitably, it becomes difficult to melt-mold, and conversely if too many thermoplastic resins are used to enable melt-molding, the oil resistance and barrier properties of the starch polymer will deteriorate.
It is generally said that it is quite difficult to balance the two. However, in the present invention, such a problem can be solved by using the EVOH.

Examples of the starch-based polymer of the present invention include 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. Physically modified starch (α-starch, fractionated amylose, heat-moisture treated starch, etc.); Enzyme-modified starch (hydrolyzed dextrin, enzyme-degraded dextrin, amylose, etc.); Chemically-modified starch (acid-treated starch, Hypochlorous acid oxidized starch, dialdehyde starch and the like); chemically modified starch derivatives (esterified starch, etherified starch, cationized starch, crosslinked starch and the like) and the like are used. Among the chemically modified starch derivatives, esterified starch includes acetate esterified starch, succinate esterified starch, nitrate esterified starch, phosphate esterified starch, urea phosphate esterified starch, xanthate esterified starch, and acetoesterified starch. As etherified starch such as acetate esterified starch, allyl etherified starch, methyl etherified starch, carboxymethyl etherified starch, hydroxyethyl etherified starch, hydroxypropyl etherified starch and the like, and as cationized starch, starch and 2 -Formaldehyde cross-linked starch as cross-linked starch such as reaction product of diethylaminoethyl chloride, reaction product of starch and 2,3-epoxypropyltrimethylammonium chloride , Epichlorohydrin cross-linked starch, phosphoric acid cross-linked starch, acrolein cross-linked starch and the like.

Starch-based polymers are EVO as water-containing substances.
It can also be used for blending with H. The EVOH of the present invention has an ethylene content of 20 to 60 mol%, preferably 2
8 to 50 mol%, saponification degree of vinyl acetate unit 90 mol%
Above, preferably 98 mol% or more can be used.
When the ethylene content is less than 20 mol%, the melt moldability is lowered, and when it exceeds 60 mol%, the mechanical properties and the gas barrier properties are impaired, which is not practical. If the saponification degree is less than 90 mol%, the mechanical strength and the gas barrier property will be insufficient.

EVOH can be used as a water-containing material for blending with the above starch-based polymer. When used as such a water-containing material, the compatibility dispersibility with the starch-based polymer is good without using a plasticizer in combination, so that there is no bleeding due to the use of the plasticizer, and a decrease in interlayer adhesive strength is prevented. You can In this case, the water content of EVOH is 20 to 60% by weight, preferably 25 to 50% by weight. When the water content is less than 20% by weight, the effect of improving the compatibility and dispersibility with the starch-based polymer is not so remarkable, and the combined use of a plasticizer is unavoidable, so that it is meaningless to use as a water-containing material.
On the other hand, when the water content exceeds 60% by weight, foaming occurs during melt molding, which makes smooth molding difficult, or the surface characteristics of the obtained molded product deteriorate. The peak temperature (corresponding to the melting point) by DSC of the hydrous ethylene-vinyl acetate copolymer saponification product (A) having the above-specified water content is 11
The temperature is 0 ° C. or lower, particularly about 90 to 105 ° C.

EVOH having the above copolymer composition
Are, for example, other α-olefins, ethylenically unsaturated carboxylic acid compounds (acids, anhydrides, salts, esters, amides, nitriles, etc.), vinyl ethers, vinyl esters other than vinyl acetate, ethylenically unsaturated sulfonic acid compounds. It may be copolymerized and modified with a compound (acid, salt, etc.), an oxyalkylene group-containing monomer, or the like, which is “post-modified” such as oxyalkylene etherification, cyanoethylation, acetalization, urethanization, etc. Good.

EVOH is typically obtained by washing and purifying powder, particles or pellets of saponified ethylene-vinyl acetate copolymer after alkali-saponifying an ethylene-vinyl acetate copolymer having the above-specified ethylene content. It is obtained by doing. In the case of washing and purification, it is obtained by thoroughly washing with an acid, especially an aqueous solution of a weak acid or a dilute strong acid (or an acid salt thereof), and further by washing with water to remove the acid adhering to the resin and then drying. Be done.

Here, as the weak acid, acetic acid, propionic acid, glycolic acid, lactic acid, adipic acid, azelaic acid,
Glutaric acid, succinic acid, benzoic acid, isophthalic acid, and terephthalic acid are usually used, and those having a pKa (25 ° C.) of 3.5 or more are used. Examples of the strong acid include organic acids having a pKa (25 ° C.) of 2.5 or less such as oxalic acid and maleic acid, and inorganic acids such as phosphoric acid, sulfuric acid, nitric acid and hydrochloric acid, and acid salts of these strong acids can also be used. it can. Treatment with a strong acid (or an acid salt thereof) is performed after treatment with a weak acid.
It is usually performed before or after washing with water.

The blending ratio of the starch polymer and EVOH is preferably 80:20 to 20:80, particularly 70:30 to 30:70 on a dry basis. If the proportion of the starch-based polymer is too low, the physical properties required as starch will be poor, while if the proportion is too high, the melt moldability of the composition will be insufficient. However, depending on the application, there may be some deviation from the above blending ratio.

The composition of the present invention further comprises a polyhydric alcohol (glycerin, trimethylolpropane, pentaerythritol, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol,
Polypropylene glycol, mannitol, sorbitol, etc.) or a plasticizer such as urea or water may be added in an appropriate amount so as not to impair oil resistance and gas barrier properties. However, when a water-containing starch polymer or water-containing EVOH is used, Smooth melt molding can be performed with or without addition. In addition, if necessary, resin components other than the above (polyvinyl alcohol and its derivatives, ethylene copolymers and other polyolefins, hydrogenated styrene-butadiene rubber, polyurethane, polyamide, polyhydroxybutyrate, etc.) and starch-based polymers other than Natural polymers (polysaccharide-based polymers, cellulose-based polymers, protein-based polymers, etc.), heat stabilizers, autoxidizers, fillers, colorants, water-proofing agents and the like can also be appropriately added.

Examples of other substrates to be laminated with the layer of the composition of the present invention include thermoplastic resin, paper such as kraft paper, cloth such as woven cloth and non-woven cloth, metal foil, wood and the like. As the thermoplastic resin, polyolefin resin, vinyl alcohol resin, acrylic resin, polyamide resin, polyester resin, polyurethane resin, polystyrene resin, polyacetal resin, polycarbonate resin, diene resin, cellulose resin And so on.

Among these thermoplastic resins, at least one photodegradable polymer selected from the group consisting of ethylene-carbon monoxide copolymer, ethylene-vinyl ketone copolymer, polybutadiene and isoprene rubber. , Or a polyolefin-based photodegradable polymer prepared by blending at least one of these, further a transition metal, or a photodegradable polymer imparted with photodegradability by blending a photosensitizer as a base material. When used, the layer of the composition of the present invention exhibits biodegradability, so that the laminated structure of both exhibits natural disintegration as a whole, and also paper, woven fabric of natural cellulose fiber, non-woven fabric, wood board, etc. The laminated structure of and will show biodegradability and disintegration as a whole, and will be more useful in industry.

The ethylene-carbon monoxide copolymer is obtained by copolymerizing ethylene and carbon monoxide at high temperature and ultrahigh pressure, and the copolymerization ratio of carbon monoxide is 0.3 to 10.
It is often set to about weight%. Examples of the ethylene-vinyl ketone copolymer include ethylene-methyl vinyl ketone copolymer and ethylene-methyl propyl ketone copolymer. The copolymerization ratio of vinyl ketone is often about 0.1 to 10 mol%, but the copolymerization ratio can be further increased. Examples of the polybutadiene include thermoplastic 1,2-polybutadiene, high cis-butadiene rubber, low cis-butadiene rubber, and the like, but thermoplastic 1,2-polybutadiene in which butadiene is bonded at 90% or more 1,2-polybutadiene is particularly preferable. preferable. As isobrene rubber,
Natural rubber, natural trans-polyisoprene, modified natural rubber, isoprene rubber, trans-polyisoprene and the like are used, and natural rubber is particularly important.

These ethylene-carbon monoxide copolymers,
Ethylene-methyl vinyl ketone copolymer, ethylene-methyl propyl ketone copolymer, 1,2-polybutadiene, etc. as low density polyethylene, linear low density polyethylene,
A photodegradable polymer blended in an amount of 3 to 20 parts by weight with respect to 100 parts by weight of a polyolefin such as high-density polyethylene, polypropylene, or ethylene-vinyl acetate copolymer can also be used. It is also possible to use a transition metal salt or a photodegradable polymer having photodegradability provided by a photosensitizer. The transition metal salts include stearin, dialkyl thiocarbamate, salicylaldehyde, acetylacetone, benzophenone oxime, etc. Iron (II), zinc (II), manganese (II), Ni (I
I), cerium (III), cobalt (II) and the like can be used as photosensitizers such as benzophenone, acetophenone and aresolaquinone.

As a method for laminating the layer of the composition of the present invention and another substrate, a dry laminating method, an extrusion coating method,
Co-injection molding method, multi-layer inflation molding method, multi-layer T-
Any known method such as a die extrusion molding method, a multi-layer hollow molding method, and a multi-layer pipe extrusion method is adopted, and as a joining method of the molten resin layer, an in-die joining method and an outside die joining method can be adopted.

When such a laminate is produced by a melt molding method, an adhesive is preferably used, and as the adhesive layer, various types such as polyolefin type, polyester type and acrylic type are preferably used. Preferable is an acid-modified polyolefin, more preferably a carboxylic acid (for example, maleic anhydride) -modified polypropylene, a carboxylic acid-modified ethylene-vinyl acetate copolymer. Such an adhesive layer is usually used in a thickness of 5 to 50 μ. Also,
As the anchor coating agent used in the dry laminating method, various types such as isocyanate type, polyethyleneimine type, polybutadiene type, and organic titanium type are suitably used, and usually coated with a thickness of 0.5 to 2 μ. Used.

Taking advantage of its oxygen barrier property, the starch-based polymer laminated structure of the present invention is molded into a container of any shape such as a bag, a bottle, a cup, a tube or a tray, and used as a packaging material or the like. When a photodegradable polymer or paper is used as the base material, disintegration can be imparted to the entire molded product,
Further, the usefulness for the above-mentioned uses is increased.

[0021]

[Working] In the starch-based polymer laminated structure of the present invention, the combined use of EVOH has the effect of imparting melt-moldability to the starch-based polymer so that the laminated structure can be easily produced.

[0022]

EXAMPLES The present invention will be described in more detail below with reference to examples. The main purposes of Examples and Comparative Examples are as follows. ○ Examples 1 to 7 are raw starch-EVOH having various compositions
A laminate of a film and a thermoplastic resin film or paper was manufactured, and the oxygen permeability, the interlayer adhesive strength, etc., for each humidity were examined. Of these, Examples 1 to 4 used a photodegradable polymer as the thermoplastic resin. ○ Comparative Example 1 is to investigate how the enzyme barrier property of a laminate with a base material using only starch is affected by humidity (water resistance). ○ Comparative Example 2 shows that even if a laminate is produced by melt molding using a resin other than EVOH, the enzyme barrier property which is a characteristic of starch is not utilized.

<Laminate Structure with Thermoplastic Resin> ⊚ Production of EVOH and Pellets thereof EVOH and pellets thereof having various ethylene contents, saponification degrees and water contents were produced. First, the ethylene content is 28.
0 mol%, 38.0 mol%, 44.0 mol% or 47.0
A methanol solution of sodium hydroxide as a catalyst was added to a methanol solution of ethylene-vinyl acetate copolymer that is mol% to carry out a continuous saponification reaction in a tower, and water was added to the obtained methanol solution of the saponified product. After forming a methanol-water mixed solvent solution, it was discharged from a nozzle into water at 20 ° C or lower. As a result, the solution was solidified into a strand having a diameter of about 3 mm, and the solidified product was pulled up from water and cut. Next, this strand-shaped coagulated product is pelletized by a pelletizer, sodium acetate contained in the polymer is removed by washing with water, further washed with a dilute aqueous solution of acetic acid, and then washed with a dilute aqueous solution of phosphoric acid, and then variously dried. It was dried under the conditions and adjusted to the target water content. EV obtained
OH pellets (A-1) to (A-5) composition, water content,
The melting point (peak temperature by DSC) is shown in Table 1.

Table 1 A-1 A-2 A-3 A-4 A-5 Ethylene content (mol%) 44.2 27.8 38.2 46.8 44.2 Degree of saponification (mol%) 99. 5 99.5 99.4 99.2 99.5 Moisture content (wt%) 26 40 35 40 0.6 Melting point (° C) 100 95 97 93 93 164

Film Formation of Starch Polymer-EVOH Composition Here, starch polymer-EVOH is used on a dry weight basis.
Pellets with various compositional ratios of OH were produced and further filmed. That is, the EVOH pellets (A
-1) to (A-5), raw starch (corn starch having a water content of 12% by weight) and, if necessary, glycerin as a plasticizer at a ratio and combination shown in Table 2 to be described later into a Henshur mixer. Mix and feed to an open vent twin-screw extruder, temperature 1 when using hydrous EVOH.
At 20 ° C., when dry EVOH with a water content of 0.6% was used, it was extruded linearly at 170 ° C. and pelletized. Then, the pellets are supplied to a single-screw extruder and extruded from a T-die under the conditions of a cylinder temperature of 140 ° C. or lower and a die temperature of 140 ° C. or lower, and films (B-1) to (B-
5) was produced. Further, the film using water-containing EVOH was formed into a T-die film and then passed through a hot air circulation drying furnace at 150 ° C. to adjust the water content of the film to 7% or less. Table 2 also shows pellet processability, its composition, and film processability.

Film formation of a film for a base material: Various materials and formulations described in Examples are supplied to a single-screw extruder, a cylinder temperature is 200 to 230 ° C., and a die temperature is 20.
Films (C-1) to (C-5) having a thickness of 50 μm were extruded from a T-die under the condition of 0 to 220 ° C.

Table 2 Film forming example 1 2 3 4 5 Used EVOH A-1 A-2 A-3 A-4 A-5 Blending ratio (parts by weight) EVOH 67.6 108.3 84.6 58.3 50 .3 Raw starch 56.8 39.8 51.1 73.9 56.8 Glycerin --- 1935 Pellet processability Good Good Good Good Good Composition of processed pellets (wt%) EVOH 42.1 46.6 42. 2 25.6 36.0 Raw starch 42.1 25.1 34.6 47.4 36.0 Water 15.8 28.3 23.2 20.2 4.1 Glycerin --- 6.8 23.9 Raw starch / EVOH 50/50 35/65 55/45 65/35 50/50 Dry weight ratio Good film processability Good Good Good Good Good Film No. B-1 B-2 B-3 B-4 B-5

Production of Laminated Structure and Measurement of Physical Properties and Disintegration Example 1 Starch polymer-EVOH film (B-1) and ethylene-carbon monoxide copolymer film (C-1) were used as anchor coating agents. As an isocyanate type (D), the layer structure and film thickness (μ) are (B-1) / (D) / (C-1) =
A 35/1/50 two-layer laminated structure was produced by dry lamination. Some were thinned by heat treatment. The oxygen permeability of such a laminated structure is low humidity (25 ° C, 30% R
H) 0.5 cc / m ² · 24 hr · atm, high humidity (25 ℃, 7
At 5% RH), it was 1.5 cc / m ² · 24 hr · atm, and the interlayer adhesive strength was 850 g / 25 mm width.

Examples 2 to 6 Instead of the film (B-1) in Example 1, (B-2) to
(B-5) and 10% by weight of ethylene-methyl vinyl ketone 5 mol% copolymer instead of the film (C-1).
Blended low density polyethylene film (C-2),
High density polyethylene film (C-3) blended with 10% by weight of thermoplastic 1,2-polybutadiene, linear low density polyethylene film (C-4) blended with 0.5% by weight of ferric stearate, surface A laminated structure was produced in the same manner as in the same example using each film of the polyethylene film (C-5) that was subjected to corona treatment, and the physical properties and the disintegration property of the film when left on soil were measured. The layer structure and the measurement results are also shown in Table 3.

[0030]Table 3 Example 1 2 3 4 5 6  Layer structure Raw starch-EVOH B-1 B-2 B-3 B-4 B-1 B-5 filmOther base film C-1 C-2 C-3 C-4 C-5 C-5  Oxygen permeability *¹ (Cc / m²・ 24hr ・ atm) 30% RH, 25 ℃ 0.5 0.3 0.4 1.5 0.5 0.5 5075% RH, 25 ° C 1.5 1.0 1.7 7.3 1.6 300 Interlayer adhesion *² 850 830 760 530 860 50(G / 25mm width) Natural disintegration on soil * ³ Yes Yes Yes Yes Yes No No No

* 1 Measurement of Oxygen Permeability According to ASTM D 3985, OX-TRAN100 type manufactured by Modern Control Co. is used, and 30% at 25 ° C.
Measured at RH and 75% RH. * 2 Interlayer adhesive strength measurement method Measure the adhesive strength between the raw starch-EVOH layer and other base material layers according to JIS
It was measured according to Z 0237. * 3 Disintegration measurement The disintegration of the laminated films produced in Examples 1 to 4 was examined. The measuring method was a film measuring 1 m in length and 1 m in width, and the film was placed so that the surface of the raw starch-EVOH layer was in contact with the ground, and the film state was visually observed after 6 months and 1 year. As a result, in the films of Examples 1 to 4 in which the polyolefin layer was provided with photodegradability, a large number of cracks occurred after 6 months.
A year later, the film collapsed, leaving no shape.
Example 5 in which photodegradability is not imparted to the polyolefin layer
In the films of ~ 6, the starch EVOH layer was almost peeled off and disintegrated after 1 year, but the shape of the polyolefin layer remained.

Example 7 Raw starch-EVOH film (B-1) and thickness 30 μm
The kraft paper of No. 1 was laminated by hot pressing, and the physical properties were measured. Oxygen permeability is 30% RH, 0.5cc / m ^{2 at} 25 ℃
・ 24hr ・ atm, 75% RH, 25cc, 1.6cc / m ²・ 24
Since it was hr · atm, the interlayer adhesive force could not be measured because the graft paper was broken during the measurement. As for the disintegration property, a large number of cracks and holes were generated after 6 months, and the shape did not remain after 1 year.

Comparative Example 1 A 50 .mu.m thick polyethylene film (C-5) coated with an anchor coating agent was coated with raw starch (water content of 12% by weight corn starch) by a casting method to obtain a water content of 7% by weight. A 35μ thick starch layer was molded. The oxygen permeability of this laminated film is 2.0 cc at 30% RH and 25 ° C.
/ M ² · 24hr · atm, 75% RH, 70cc / m ^{2 at} 25 ° C
・ 24 hr ・ atm, interlayer adhesion was 0 g / 25 mm width, easy peeling, and starch film was easily broken.

Comparative Example 2 80 parts by weight of low-density polyethylene (F-161, Mitsubishi Kasei Co., Ltd.) having a melt index of 6 g / 10 min and 20 parts by weight of raw starch (corn starch having a water content of 12% by weight) were mixed with a Henschel mixer. Then, it is supplied to an extruder to be pelletized once, and then the pellets are supplied to the extruder and extruded from a T-die under the conditions of a cylinder temperature of 190 ° C. and a die temperature of 180 ° C., and a film having a thickness of 30 μm (B-
6) was obtained. If the blending amount of raw starch was further increased, film formation was impossible. Physical properties were measured by laminating the film (B-6) and a polyethylene film (C-5) having a thickness of 30 μm using an isocyanate type as an anchor coating agent by a dry lamination method. Oxygen permeability is 1000cc / m ² · 24hr · atm or more at 30% RH, 25 ° C, 1000cc / m ² · 24hr · at at 75% RH, 25 ° C
It was m or more and the interlayer adhesion was 850 g / 25 mm width.

[0035]

The starch-based polymer laminated structure of the present invention is obtained by adding EVOH to a starch-based polymer.
Since its melt moldability is improved, a laminated structure can be easily produced, and it has an effect that it can be utilized in a wider range of applications by taking advantage of the barrier property and oil resistance of starch.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location C08L 23/26 LDM 7107-4J

Claims (4)

[Claims] 1. A starch-based polymer laminated structure obtained by laminating a layer of a composition comprising a starch-based polymer and a saponified ethylene-vinyl acetate copolymer and another substrate. 2. The starch-based polymer laminated structure according to claim 1, wherein the other base material is a thermoplastic resin. 3. The thermoplastic resin is at least one photodegradable polymer selected from the group consisting of ethylene-carbon monoxide copolymers, ethylene-vinyl ketone copolymers, polybutadiene and isoprene rubbers, or at least these. The starch-based polymer laminated structure according to claim 2, which is a polyolefin-based photodegradable polymer prepared by blending one kind. 4. The starch-based polymer laminate according to claim 2, wherein the thermoplastic resin is a photodegradable polymer imparted with photodegradability by blending a transition metal or a photosensitizer.