KR100527652B1 - A thermoplastic resin composition and moulded articles - Google Patents

Abstract

SUMMARY OF THE INVENTION An object of the present invention is to provide a resin composition capable of controlling a wide range of water vapor permeability while maintaining high gas permeability, a molded article or packaging material containing the composition, and particularly a food packaging material such as fruits and vegetables.

The present invention provides a polymer (A) containing a polyether chain as a structural unit, a polyethylene (B) having a density of less than 0.91 g / cm 3 as measured according to JIS K6760, and a compatibilizer (C) of A / B / C = 99.5 to Thermoplastic resin composition, characterized in that it is mixed at a weight ratio (A + B + C = 100) of 0.5 / 0.5 to 99.5 / 0 to 30, molded articles comprising the composition, in particular for the cultivation or packaging for food storage of vegetables and fruits It is about.

Description

Thermoplastic composition and molded article {A THERMOPLASTIC RESIN COMPOSITION AND MOULDED ARTICLES}

The present invention relates to a thermoplastic resin composition and molded articles thereof. SUMMARY OF THE INVENTION An object of the present invention is to provide a resin composition capable of controlling a wide range of water vapor permeability while maintaining high gas permeability, a molded article or packaging material containing the composition, and particularly a food packaging material such as fruits and vegetables.

Thermoplastic resins such as polyolefins have been used in a variety of applications until now due to their ease of handling and good balance of properties, and are also valuable as packaging materials. Under these circumstances, depending on the resin used, various types of materials can be devised and used for specific purposes, from permeable films with high gas permeability to barrier materials with low permeability but very few with high water vapor permeability. have. For example, a technique of mixing and laminating a high permeability material and a low permeability material is known. However, when storing food products using this technique, problems such as condensation of water vapor and adhesion of water droplets occur, and the inside cannot be observed, or condensed water promotes deterioration of the contents, causing corruption. There is a tendency. Moreover, there are limitations to controlling the gas permeability upon storage for long periods of time.

For the purpose of solving such a problem, a method of controlling the transmittance by the diameter and the density of the hole is known by making a fine hole in the film mechanically by a needle or the like by physically or by a laser (for example, Japanese Patent Laid-Open). Publications 47-23478, 62-148247 and 2-85181, etc.). In addition, instead of puncturing the film, a method of increasing the water vapor transmission by locally forming a very thin area in the film has been proposed. However, in these methods, significant permeability difference occurs between the minute hole area and other areas, making it difficult to obtain uniformity throughout the film, and also causing problems such as weakening of the film strength and low selectivity of the transmittance.

On the other hand, no other attempts are made at all to increase the permeability of the film itself, so that a gas for controlling metabolism is collected inside, and instead a method of injecting an adsorbent of harmful gases and moisture (e.g., Japanese Patent Laid-Open No. 3-14480, etc.). However, this method is tricky, and moreover, the effect is not necessarily appropriate.

At present, compositions comprising polyether containing block polyamides and the like and polyolefins and / or functional polyolefins are already known (e.g., Japanese Patent Laid-Open Publication Nos. 1-163234, and European Patent Publications 459862, 475963, 559284, 657502 and 675167 and the like). Regarding the effect, the patent discloses moisture permeability, high impact elasticity, antistatic property and the like. However, these patents only disclose the general content of polyolefins and do not mention anything about the density of polyolefins for controlling gas permeability.

[Problem to Solve Invention]

The present invention is based on the finding that in attempts to control water vapor permeability within the desired range while maintaining high gas permeability, this can be achieved by incorporating a resin having a certain density.

[Means for solving the problem]

The present invention relates to a polymer (A) containing a polyether chain as a structural unit, a copolymer (B) having a density of less than 0.91 g / cm 3 as measured according to JIS K6760, polyethylene or polyethylene, as a main component, and a compatibilizer ( C) is mixed in a weight ratio (A + B + C = 100) of A / B / C = 99.5 to 0.5 / 0.5 to 99.5 / 0 to 30, and a molded article or packaging material thereof. .

In the present invention, "polymer (A) containing a polyether chain as a structural unit" means a block copolymer in which a polyoxyalkylene chain and other polymer chains are bonded to each other, or polyoxyalkylene chains are used to form a coupling site. It means a polymer bonded to each other through. Examples of the polyoxyalkylene include polyoxyethylene, poly (1,2- and 1,3-oxypropylene), polyoxytetramethylene, polyoxyhexamethylene, block or random copolymers of ethylene oxide and propylene oxide, ethylene Block or random copolymer of oxide and tetramethylene oxide. In particular, those having a C _2-4 alkylene moiety are preferred, with polyoxyethylene being most preferred. The number average molecular weight of the polyoxyalkylene is 200 to 6,000, preferably 300 to 4,000.

Preferred "polymers (A) containing polyether chains as structural units" used in the present invention are polyether-polyamide block copolymers, polyether-polyester block copolymers or polyether-urethanes. Of these, polyether-polyamide block copolymers are particularly preferred.

The "polyether-polyamide block copolymer" used in the present invention is a polymer in which a polyoxyalkylene chain (a) and a polyamide chain (b) are bonded to each other, wherein the chain (b) has 6 or more carbons. Polymers of aminocarboxylic acids or lactams, or polymers of salts of dicarboxylic acids and diamines having at least six carbons. When the chains (a) and (b) are bonded to each other via a C _4-20 dicarboxylic acid, the materials are usually regarded as polyetheresteramides, which are also within the scope of the present invention. "Aminocarboxylic acid or lactam having 6 or more carbons, or a salt of dicarboxylic acid and diamine having at least 6 carbons" includes 11-aminoundecanoic acid, 12-aminododecanoic acid, caprolactam, lau Lolactam, hexamethylenediamine / adipic acid salt, or hexamethylenediamine / sebacinate salt etc. are used preferably. Moreover, 2 or more types of said (a) and (b) component can be used together.

The polymer is produced by, for example, the method disclosed in Japanese Patent Publication No. 56-45419. Specific examples of the polymer include Pebax (Elf Atochem), ELY (EMS) and Vestamid (Hols). The kind and weight ratio of the polyether component and the polyamide component in the block copolymer used in the present invention are selected according to the purpose and use. From the viewpoint of water vapor permeability, water resistance and ease of handling, the ratio of polyether / polyamide is preferably 4/1 to 1/4.

The "polyether-polyester block copolymer to be used" in the present invention is a polymer in which a polyoxyalkylene chain (a) and a polyester chain (d) are bonded to each other, and the polyester has a hydride having 6 or more carbons. Polymers of oxycarboxylic acids, or dihydroxy compounds having two or more carbons and polymers of aromatic dicarboxylic acids. Moreover, 2 or more types of these (a) and (d) component can be used together. Such polymers are prepared, for example, by the method disclosed in US Pat. No. 4739012. Specifically, Hytrel (DuPont), Pelprene P type (Toyobo) and Rekuse (Teijin) can be cited. The weight ratio of the above components (a) and (d) in the block copolymer used in the present invention will be determined according to the purpose and use. Thermoplastic polyester elastomers are provided in the same way, but with little effect as polyester-polyester block copolymers (eg Pelprene S type).

"Polyether-urethane" as used herein is a thermoplastic polyurethane in which polyether is used as a soft segment. There is little effect with polyester type or caprolactone type polyurethanes. Specifically, the polyether-urethane is usually obtained by the reaction of an organic diisocyanate with a polyether having a molecular weight of 500 to 6,000, in which case chain expansion occurs in the presence of a catalyst.

As the isocyanate, tolylene diisocyanate or diphenylmethane diisocyanate is preferably used, and as polyether, polytetramethylene glycol, polypropylene oxide or polyoxyethylene is preferably used.

In the present invention, these polyether-polyamide block copolymers, polyether-polyester block copolymers or polyether-urethanes may be used alone or as a mixture of each other, or in the case of block copolymers, Mixtures of two or more polymers that are different and / or differ in the soft / hard segment ratio in each resin can be used, or a mixture with other resins in an amount sufficient to realize the object of the present invention. have.

In the present invention, "polyethylene or copolymer (B) having a density of less than 0.91 g / cm 3 as measured according to JIS K6760, the main component of which is polyethylene" is 10 to 20 mol% or less with ethylene homopolymer or ethylene. It is considered as a copolymer of an α-olefin monomer (comonomer), wherein the polymer or copolymer has a density measured according to JIS K6760 of less than 0.91 g / cm 3. Thus, ordinary general purpose polyethylenes, ie polyethylenes having a density of at least 0.91 g / cm 3 as measured according to JIS K6748 or ASTM D1248, are not included, which are outside the scope of the present invention. The density is also preferably less than 0.90 g / cm 3.

Polyethylene or copolymers in which the polyethylene is a main component are conventionally known polymerization methods, ie high pressure radical polymerization methods under oxygen or peroxide catalysts, medium / low pressure under Ziegler-Natta catalysts or silica- or alumina-supported catalysts. Homopolymerization of ethylene or co-polymerization of ethylene by coordination polymerization method or polymerization method under " single site catalyst (SSC) " having a uniform activity point represented by a Kaminsky type metallocene catalyst (ethylene and α-olefin monomers (comonomers) ) (E.g., propene, butene, hexene, octene, decene or 4-methyl-1-pentene, etc.). Examples of the ultra low density polyethylene or copolymers of which polyethylene is the main component include Rumitakku 9P107T or 43-1 (Toray), Eboryu SP0540 (Mitsui Petrochemical), Engage EG8150 or 8100 (Dow Chemical), and Affinity PF1140, PL1880 or FW1650 ( Dow Chemical).

Among them, for a given density, a copolymer in which polyethylene of a single site catalyst system or polyethylene is a main component is particularly preferable.

In the present invention, a compatibilizer (C) may be used depending on the situation. In the present invention, "compatibility agent (C)" is a polymer used to improve the miscibility between a polymer (A) containing a polyether chain as a structural unit and a polyethylene (B) having a density of less than 0.91 g / cm 3, Polycarboxylic acids grafted or copolymerized with unsaturated carboxylic acids, unsaturated carboxylic anhydrides or unsaturated epoxides or (meth) acrylates or vinyl acetate copolymers thereof ". Specific examples thereof include maleic anhydride graft polyethylene or polypropylene, ethylene / maleic anhydride copolymers, ethylene / alkyl acrylate / maleic anhydride terpolymers, ethylene / vinyl acetate / maleic anhydride terpolymers and ethylene / alkyl acrylics Latex / glycidyl methacrylate terpolymers.

The mixing ratio (weight ratio) of the polymer (A) containing the polyether chain as a structural unit, the copolymer (B) having a density of less than 0.91 g / cm 3, the main component of polyethylene or polyethylene, and the compatibilizer (C) are A / B / C = 99.5 to 0.5 / 0.5 to 99.5 / 0 to 30, preferably 95 to 5/5 to 95/1 to 20. For storage of items that exhibit significant gout action, the above A / B / C = 99 to 55/1 to 45/0 to 30, preferably 90 to 60/10 to 40/1 to 20, is recommended and relatively quickly For storage of the item to be dried, A / B / C = 45 to 1/55 to 99/0 to 30, preferably 40 to 5/60 to 95/1 to 20 is recommended. Under these circumstances, in each case A + B + C = 100. By mixing these components in the above ratio, it becomes possible to control the water vapor permeability extensively while maintaining high gas permeability.

With respect to the resin composition, each resin may be dry mixed in a specific ratio and then extruded immediately to prepare a molded article, or prior to molding, (A), (B) or (C) may be melt mixed in advance to form pellets. Alternatively, the molded article may be prepared by mixing (A) and (C) or (B) and (C) in advance and then extruding or injection molding the mixture with (B) or (A) during molding. have. In other words, a so-called masterbatch method can also be used. The melt mixing is performed using a conventional single screw or twin screw extruder or the like. The melting temperature depends on the type and ratio of the resin, but is usually 120 to 230 ° C.

In the resin composition of this invention, a well-known antioxidant, a thermal decomposition inhibitor, a ultraviolet absorber, a hydrolysis improving agent, a coloring agent (dye and pigment), an antistatic agent, an electrically conductive agent, a crystal nucleating agent, a crystallization promoter, a plasticizer, and an easy slid Agents, lubricants, mold release agents, flame retardants, flame retardant aids and the like can be freely contained within the scope of not impairing the properties of the present invention.

The resin composition of the present invention can be used by itself to produce an extruded article such as a sheet, a film or a tube, or an injection molded article such as a container, and may also be used after being mixed with other thermoplastic resins. When producing an extruded article, inflation as well as various other means such as a T-die system can be used.

Next, the present invention will be described in more detail with reference to the following examples. However, it should not be construed that the present invention is limited to these examples. In addition, various characteristic values in the following Examples were measured by the following method.

(1) Density (unit: g / cm 3)

Measured according to JIS K6760.

(2) MFI (melt flow index) (unit: g / 10 min)

According to JIS K6760, it measured at a load of 2.16 kg and 190 degreeC.

(3) intrinsic viscosity (unit: g / dl)

Calculated from the viscosity of the solution measured at 20 ° C. using the m-cresol solution of the polymer.

(4) Moisture Permeability (Water Vapor Permeability) (Unit: g / ㎡ · day)

Under conditions B (40 ° C., 90% relative humidity), the film was measured according to JIS Z0208.

(5) Gas permeability (unit: ml / m2 · day · atm)

Measured by the method using pressure difference.

Specific conditions were as follows:

Device: Gas Permeability Measuring Device Model GTR-10XE (Yanako Bunseki Kogyo Co.)

Test Area: 15.2 cm 2 (44 mm diameter)

Detection method: Operating curve system by gas chromatography with TCD

Temperature, relative humidity: 25 ℃, 0% RH

Carrier gas: helium, 70 KPa

Diffusion Gas: CO ₂ / O ₂ / N ₂ / C ₂ H ₄ (30.0 / 30.0 / 39.12 / 0.88% by volume)

In addition, the resin used was as follows:

A-1: polyetheresteramide having an intrinsic viscosity of about 1.5, comprising a polyoxyethylene chain (average molecular weight 1500) and a polyamide 12 chain (average molecular weight 1500)

A-2: polyetheresteramide having an intrinsic viscosity of about 1.5, comprising a polyoxyethylene chain (average molecular weight 1,500) and a polyamide 12 chain (average molecular weight 4,500)

A-3: polyetheresteramide containing polyoxyethylene chain (average molecular weight 1,500) and polyamide 6 chain (average molecular weight 1,500)

B-1: polyethylene having MFI 5 and density 0.87, obtained by polymerization with a metallocene catalyst

B-2: polyethylene having MFI 1.6 and density 0.895, obtained by polymerization with a metallocene catalyst

B-3: polyethylene having MFI 4 and density 0.905, obtained by polymerization with a metallocene catalyst

B-4: polyethylene having MFI 8 and density 0.905, obtained by radical polymerization

B-5: polyethylene having MFI 4 and density 0.920, obtained by polymerization with a metallocene catalyst

B-6: polyethylene having MFI 4 and density 0.920, obtained by radical polymerization

C-1: ethylene / acrylate / maleic anhydride terpolymer containing 6% by weight comonomer and 3% by weight maleic anhydride

C-2: Ethylene / glycidyl methacrylate copolymer containing 8% by weight of glycidyl methacrylate

Examples 1 to 6 and Comparative Examples 1 and 2

Resin A, B and C were mixed at a weight ratio A / B / C = 30/55/15, and then melt-extruded with a twin screw extruder set at 160 to 180 ° C. to obtain compositions 1 to 8, and then pellets were prepared. It was. A 25 μm thick film was obtained from the pellets using a single screw extruder with a T-die with the tip temperature set at 180 ° C. The properties of the film in each case are shown in Table 1 below. When the films were prepared from the compositions 7 and 8 using polyethylene having a density of at least 0.91, the moisture permeability was almost the same, but the gas permeability was slightly poor (Comparative Examples 1 and 2). In addition, for polyethylenes of the same density, the material polymerized with the single site catalyst showed somewhat better gas permeability (Controls 5 and 6; Comparative Examples 1 and 2).

Composition number A B C Moisture permeability CO ₂ gas permeability Oxygen gas permeability Example 1 Composition 1 A-1 B-2 C-1 140 105,000 18,100 Example 2 Composition 2 A-2 B-2 C-1 125 72,400 15,200 Example 3 Composition 3 A-2 B-2 C-2 130 73,000 15,500 Example 4 Composition 4 A-2 B-1 C-1 170 105,200 23,000 Example 5 Composition 5 A-2 B-3 C-1 80 65,000 13,300 Example 6 Composition 6 A-2 B-4 C-1 90 60,000 12,300 Comparative Example 1 Composition 7 A-2 B-5 C-1 70 43,700 8,800 Comparative Example 2 Composition 8 A-2 B-6 C-1 85 41,500 8,400

Example 7 and Comparative Examples 3 to 5

The films prepared from Compositions 2 and 8 were cut to A4 size and in each case, two pieces were stacked on top of each other and three sides were heat sealed to prepare a bag. A bunch of grapes (Kyoho grapes) (about 500 g) was placed in and the last edge was heat sealed. For comparison, grape bunches were packaged in the same manner as above, using a paper bag of the kind used for grape cultivation and also a commercially available 25 μm thick low density polyethylene bag. Bags containing grapes were stored in the refrigerator at 5 ° C. for 1 month, and then collected and inspected for contents. In the case of the paper bag, the stems turned brown, and it was found that individual grape grains tended to fall off from the grape bunches (Comparative Example 3). In addition, in the case of a commercially available polyethylene bag, numerous drops of water were attached to the bag and found that white mold was growing in the grapes (Comparative Example 4). Moreover, the grape bunches packaged with the film bags from composition 8 looked basically good, while some of the aroma of the grapes was lost (with a slight alcohol odor) (Comparative Example 5). In contrast, in the case of grape bunches packaged with a film bag from composition 2, the stem was still fresh green and the aroma of the grape was also good (Example 7).

Example 8 and Comparative Example 6

In the same manner as in Example 1, a film having a composition of A / B / C = 65/25/10 (weight ratio) was prepared, and its properties are shown in Table 2 below. It can be observed that although the film samples have almost the same moisture permeability, the high density polyethylene based film has a lower gas permeability.

Composition number A B C Moisture permeability CO ₂ gas permeability Oxygen gas permeability Example 8 Composition 9 A-2 B-2 C-1 780 54,900 7,000 Comparative Example 6 Composition 10 A-2 B-6 C-1 800 43,000 5,000

Example 9 and Comparative Example 7

To add 22 peaches, the lid was removed from the corrugated cardboard box and 22 peaches were loaded into the box as soon as they were picked from the tree. The whole pack was then wound up with a film or nylon film from Example 8 and then heat sealed. After holding at room temperature (23 ° C) for 7 days, the gas inside the pack was taken out and analyzed, and then the pack was opened to evaluate the contents. All of the peaches packaged using the film from Example 8 still had a good appearance, no abnormalities when cut inside with a kitchen knife, and tasted excellent. In addition, the gas concentration inside the pack was carbon dioxide = 6% and oxygen = 7% (Example 9). On the other hand, with respect to the peach packaged using the nylon film, three of the 22 peaches were damaged and blackened, and the alcohol smell was considerable. The gas concentration inside the pack was carbon dioxide = 15% and oxygen = 12%, and due to the low gas permeability, it could be estimated that there was some anaerobic fermentation (Comparative Example 7).

As described above, the composition of the present invention is mixed with a polymer having a polyether chain and a copolymer having a certain density of a certain proportion of polyethylene or polyethylene, thereby maintaining a high gas permeability while It is possible to obtain shaped articles having a wide range of water vapor transmission, and in particular to provide packaging for the cultivation or storage of fruits and vegetables.

Claims (9)

Polymers (A) containing polyether chains as structural units, copolymers (B) having a density of less than 0.91 g / cm 3 as measured according to JIS K6760, polyethylene or polyethylenes as main components, and compatibilizers (C) A / B / C = 99.5 to 0.5 / 0.5 to 99.5 / 0 to 30, mixed in a weight ratio (A + B + C = 100), and the carbon dioxide permeability is greater than about 54,900 ml / m ² .atm.day And, the oxygen transmission rate is greater than about 7,000 ml / m ² .atm. Day. 2. The polymer according to claim 1, wherein the polymer (A) containing a polyether chain as a structural unit is selected from the group consisting of polyether-polyamide block copolymers, polyether-polyester block copolymers, and polyether-urethanes. Thermoplastic resin composition characterized by the above-mentioned. 3. The thermoplastic resin composition according to claim 2, wherein the polyether chain is a polyoxyethylene chain. The thermoplastic resin composition according to claim 1, wherein the density of the copolymer (B) in which polyethylene or polyethylene is a main component is less than 0.90 g / cm 3. The thermoplastic resin composition according to claim 1, wherein polyethylene or copolymer (B) in which polyethylene is a main component is produced using a single site catalyst. The group according to claim 1, wherein the compatibilizer (C) consists of a polyolefin graft or copolymerized with an unsaturated carboxylic acid, an unsaturated carboxylic anhydride or an unsaturated epoxide or a (meth) acrylate or vinyl acetate copolymer thereof. Thermoplastic resin composition, characterized in that at least one selected from. A molded article formed from the composition according to claim 1. The packaging material according to claim 7, wherein the molded article is a film, a sheet, a bag, or the like. The packaging material according to claim 8, which is for cultivation or storage of fruits or vegetables.