JP2023013692A - Resin molding - Google Patents

Abstract

To provide a resin composition that has high mechanical strength and can form a lightweight molding.SOLUTION: A resin molding is formed from a resin composition that comprises a polypropylene resin and a water-soluble polymer. In one embodiment, the water-soluble polymer is a polyvinyl alcohol resin. In one embodiment, the polyvinyl alcohol resin has a degree of polymerization of 200-2500.SELECTED DRAWING: None

Description

There is an application for the application of Article 30, Paragraph 2 of the Patent Law Exhibition date August 6, 2020 Exhibition name Package Exhibition 2020 Venue Osaka Industrial Creation Hall 3F / 4F

The present invention relates to resin moldings.

Resin moldings formed from a resin composition containing a polypropylene-based resin have been known for various uses including packaging. A resin composition further containing a filler such as talc is used. The use of a resin composition containing such fillers is advantageous in that a highly rigid resin molded article can be obtained, and the resin molded article (for example, a package) can be made thinner. On the other hand, there is an increasing demand for weight reduction of resin moldings used in various applications. When a filler is mixed as described above, there is a problem that the specific gravity of the resin molding is increased, and weight reduction is hindered.

JP 2012-251036 A JP-A-5-229078

The present invention has been made to solve the above problems, and an object of the present invention is to provide a resin molded article formed from a resin composition containing a polypropylene resin, which has excellent mechanical strength and , to provide a lightweight molded body.

The resin molding of the present invention is formed from a resin composition containing a polypropylene-based resin and a water-soluble polymer.
In one embodiment, the water-soluble polymer is a polyvinyl alcohol-based resin.
In one embodiment, the degree of polymerization of the polyvinyl alcohol resin is 200-2500.
In one embodiment, the polyvinyl alcohol resin has a saponification degree of 80 mol % or more.
In one embodiment, the water-soluble polymer is fibrous.
In one embodiment, the content of the water-soluble polymer is 1.5 parts by weight to 15 parts by weight with respect to 100 parts by weight of the total polyolefin resin.
In one embodiment, the resin composition is a resin composition obtained by melt-kneading a polypropylene-based resin and a water-soluble polymer.
In one embodiment, the resin molding has a specific gravity of 1 or less.

According to the present invention, by using a resin composition containing a polypropylene-based resin and a water-soluble polymer, it is possible to provide a molded article that is excellent in mechanical strength and lightweight.

A. Resin Molded Article The resin molded article of the present invention is formed from a resin composition containing a polypropylene resin and a water-soluble polymer. Therefore, the resin molding includes a polypropylene-based resin and a water-soluble polymer. In one embodiment, the resin composition is a resin composition obtained by melt-kneading a polypropylene-based resin and a water-soluble polymer. Preferably, the water-soluble polymer is fibrous. In one embodiment, the resin composition and resin molding may further contain a polyolefin-based resin other than the polypropylene-based resin. In one embodiment, the resin composition and the resin molding contain a polypropylene-based resin and an ethylene-based resin.

A-1. Resin Composition Typically, the resin composition is solid, and in one embodiment is provided as pellets. By using a resin composition containing a water-soluble polymer (preferably a fibrous water-soluble polymer), a resin molded article having excellent mechanical strength can be obtained. In addition, since the water-soluble polymer makes it possible to improve the mechanical strength, the use of the above resin composition makes it possible to achieve higher strength compared to resin compositions that have been strengthened by conventional fillers (e.g., glass fiber, talc, etc.). Thus, a lightweight resin molded body can be formed. That is, according to the present invention, a resin composition containing a polypropylene resin and a water-soluble polymer is equivalent to or equivalent to a resin molded product obtained from a resin composition containing a conventional filler (for example, glass fiber, talc, etc.). It is possible to obtain a resin molding that is superior in mechanical strength to the same level or more and is lighter in weight.

(polypropylene resin)
By using a polypropylene resin, it is possible to allow the water-soluble polymer to be present in the resin with good dispersibility, and the effect of including the water-soluble polymer (preferably, fibrous water-soluble polymer) becomes remarkable, and mechanical A resin molding having particularly excellent strength can be obtained. Polypropylene-based resins include polymers having 50% by weight or more of propylene-derived structural units, and include homopolymers of propylene and copolymers of propylene and other monomers copolymerizable with propylene. Other monomers copolymerizable with propylene include, for example, ethylene, 1-butene, isobutene, 1-pentene, 2-methyl-1-butene, 3-methyl-1-butene, 1-hexene, 3- methyl-1-pentene, 4-methyl-1-pentene, 1-heptene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-icosene and the like.

The content of propylene-derived structural units in the polypropylene-based resin is preferably 50 mol% or more, more preferably 80 mol% or more, more preferably 90 mol% or more, and still more preferably 95 mol% or more. Polypropylene-based resins containing many structural units derived from propylene are advantageous in that the effect of adding a water-soluble polymer is remarkable.

In one embodiment, the polypropylene resin is a block copolymer. By using a polypropylene-based resin (hereinafter also referred to as a propylene block copolymer), which is a block copolymer, it is possible to obtain resin moldings having various properties depending on the application. For example, by using a polypropylene-based resin, which is a block copolymer, it is possible to obtain a resin molding (for example, a tray for frozen foods) that is excellent in properties at low temperatures (for example, cold impact resistance).

In one embodiment, the polypropylene-based resin, which is a block copolymer, has structural units derived from ethylene. By using such a block copolymer, it is possible to obtain a resin molding having particularly excellent properties at low temperatures (for example, cold impact resistance). In one embodiment, the propylene block copolymer containing ethylene-derived structural units can be an ethylene-propylene rubber. In the propylene block copolymer containing ethylene-derived structural units (e.g., ethylene-propylene rubber), the content of ethylene-derived structural units is based on 100 parts by weight of the propylene block copolymer containing ethylene-derived structural units. , preferably 25 to 45 parts by weight, more preferably 30 to 40 parts by weight.

In one embodiment, a polypropylene-based resin having a melting point is used. The melting point of the polypropylene resin is preferably 145°C or higher, more preferably 150°C to 168°C, still more preferably 155°C to 165°C. Within such a range, a resin molding having excellent mechanical strength and excellent workability can be obtained. The melting point of the resin can be measured with a differential scanning calorimeter (DSC).

The melt flow rate of the polypropylene resin at 230° C. and 2.16 kgf is preferably 0.1 g/10 min to 50 g/min, more preferably 0.3 g/10 min to 40 g/min, still more preferably 0 .4 g/10 min to 30 g/min. Within such a range, a resin composition having particularly excellent moldability can be obtained.

The content of the polypropylene resin is preferably 50 parts by weight to 100 parts by weight, more preferably 60 parts by weight to 99 parts by weight, and still more preferably 70 parts by weight with respect to 100 parts by weight of the resin composition. to 95 parts by weight, particularly preferably 80 to 95 parts by weight. In addition, in this specification, the content ratio of each component in the resin composition may correspond to the content ratio of the component in the resin molding.

In one embodiment, a polypropylene resin A containing 80 mol % or more (preferably 90 mol % or more, more preferably 100 mol %) of structural units derived from propylene is used as the polypropylene resin. The content of the polypropylene-based resin A is preferably 80 parts by weight or more, more preferably 90 parts by weight or more, and still more preferably 100 parts by weight with respect to 100 parts by weight of the resin composition. By using the polypropylene-based resin A in such a range, it is possible to obtain a resin composition suitable for injection-molded articles (for example, toilet seats, child seats, etc.). In addition, it is possible to obtain a resin composition suitable for molded articles (for example, trays) that are used in an environment of room temperature or higher. In this embodiment, the resin composition may contain, in addition to the polypropylene-based resin A, a polyethylene-based resin described below.

In one embodiment, when the propylene block copolymer is used as the polypropylene resin, the content of the propylene block copolymer is preferably 60 parts by weight to 95 parts by weight with respect to 100 parts by weight of the resin composition. parts by weight, more preferably 70 to 90 parts by weight. By using the propylene block copolymer in such a range, it is possible to obtain a resin molding having particularly excellent properties at low temperatures (for example, cold impact resistance). In this embodiment, the resin composition may contain a polyethylene-based resin described below in addition to the propylene block copolymer.

The polypropylene-based resin may be used alone or in combination of two or more. In one embodiment, the resin composition contains polypropylene (homopolymer) and the ethylene-propylene rubber. In the present specification, such a resin composition is also referred to as a block copolymer-containing resin composition. The block copolymer-containing resin composition may contain polypropylene (homopolymer) and a polypropylene-based resin other than the ethylene-propylene rubber. In the present embodiment, the content of ethylene-propylene rubber in the resin composition (block copolymer-containing resin composition) is the total amount of the polypropylene-based resin and the polyolefin-based resin other than the polypropylene-based resin (that is, the polyolefin-based resin total amount) is preferably 15 to 30 parts by weight, more preferably 18 to 25 parts by weight, per 100 parts by weight.

The content ratio of the polypropylene-based resin is preferably 60 parts by weight or more with respect to 100 parts by weight of the total amount of the polypropylene-based resin and the polyolefin-based resin other than the polypropylene-based resin (that is, the total amount of the polyolefin-based resin), It is more preferably 65 parts by weight or more and less than 95 parts by weight, and still more preferably 70 parts by weight to 90 parts by weight. Within such a range, a resin molding having excellent mechanical properties can be obtained.

(Polyolefin resin other than polypropylene resin)
In one embodiment, the resin composition may further contain a polyolefin-based resin other than the polypropylene-based resin. That is, the resin molding may further contain a polyolefin-based resin other than the polypropylene-based resin.

Polyethylene-based resins can be preferably used as polyolefin-based resins other than polypropylene-based resins. By using a polyethylene-based resin, it is possible to obtain a resin molding having high toughness and excellent impact resistance. Polyethylene-based resins include low-density polyethylene, linear low-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-methyl (meth)acrylate copolymer, and the like. Low-density polyethylene includes ethylene homopolymers produced by high-pressure methods. Linear low density polyethylene and high density polyethylene include copolymers of ethylene and α-olefins. The comonomer α-olefin content allows the density to be controlled and can be any suitable density depending on the properties desired. Examples of α-olefins copolymerizable with ethylene include propylene, 1-butene, isobutene, 1-pentene, 2-methyl-1-butene, 3-methyl-1-butene, 1-hexene, 3-methyl- 1-pentene, 4-methyl-1-pentene, 1-heptene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-icosene and the like. The content of ethylene-derived structural units in the polyethylene resin is preferably 50 mol% or more, more preferably 70 mol% or more, still more preferably 75 mol% or more, and still more preferably 80 mol% or more.

The melt flow rate of the polyolefin resin (preferably polyethylene resin) other than polypropylene resin at 190° C. and 2.16 kgf is preferably 10 g/min or less, more preferably 0.3 g/10 min to 8 g/min. and more preferably 0.5 g/10 min to 5 g/min. Within such a range, it is possible to obtain a resin molding having excellent mechanical properties (for example, toughness).

When the resin composition contains a polyolefin-based resin other than a polypropylene-based resin, the content of the polyolefin-based resin other than the polypropylene-based resin (preferably polyethylene-based resin) is based on the total amount of the polyolefin-based resin of 100 parts by weight. , preferably 5 parts by weight or more, more preferably 5 parts by weight or more and less than 30 parts by weight, still more preferably 5 parts by weight to 25 parts by weight, and particularly preferably 5 parts by weight to 20 parts by weight. Within such a range, it is possible to obtain a resin composition which is excellent in mechanical properties (for example, toughness) and particularly excellent in moldability.

(water-soluble polymer)
A water-soluble polymer is a polymer compound that dissolves in 100 g of water at 25° C. in an amount of 1 g or more. Any appropriate water-soluble polymer can be used as the water-soluble polymer as long as the effects of the present invention can be obtained. Examples of water-soluble polymers include polymers having polar functional groups capable of hydrogen bonding, such as hydroxyl groups, carboxyl groups, amino groups, and amide groups. Specific examples of water-soluble polymers include polyvinyl alcohol-based resins, polyalkylene glycol-based resins, polyacrylamide-based resins, polymaleic acid-based resins, and cellulose-based resins.

In one embodiment, a polyvinyl alcohol-based resin is used as the water-soluble polymer. Typically, a polyvinyl alcohol-based resin is obtained by saponifying a polyvinyl acetate-based polymer.

The polyvinyl alcohol-based resin may be polyvinyl alcohol or a copolymer containing structural units derived from vinyl alcohol. Structural units other than vinyl alcohol-derived structural units (and vinyl acetate-derived structural units) contained in the copolymer (hereinafter also referred to as "other structural units") include dihydroxyalkyl groups, acetoacetyl groups, oxy Examples thereof include units having an alkylene group, a carboxy group, an alkoxycarbonyl group, and the like, and units derived from olefins such as ethylene. Specific examples of polyvinyl alcohol resins as copolymers include butenediol-vinyl alcohol copolymer (BVOH) and ethylene-vinyl alcohol copolymer (EVOH).

In the polyvinyl alcohol-based resin as a copolymer, the content of other structural units is preferably 2 mol% to 30 mol%, more preferably 5 mol% to the total structural units constituting the polyvinyl alcohol-based resin. 20 mol %.

The saponification degree of the polyvinyl alcohol resin is preferably 70 mol % or more, more preferably 80 mol % or more, still more preferably 90 mol % or more, and particularly preferably 95 mol % or more. Within such a range, the strength of the fibrous polyvinyl alcohol-based resin increases, and a resin composition that can contribute to improvement in mechanical strength can be obtained. The upper limit of the saponification degree of the polyvinyl alcohol resin is, for example, 98 mol% (preferably 100 mol%). The degree of saponification can be measured according to JIS K6726.

The degree of polymerization of the polyvinyl alcohol resin is preferably 200-2500, more preferably 200-1000, still more preferably 300-500. If it is such a range, it can be set as polyvinyl-alcohol-type resin which melt|dissolves easily. The polyvinyl alcohol-based resin is easily dispersed in fibrous form, and by using the polyvinyl alcohol-based resin, it is possible to obtain a resin composition that can contribute to improvement in mechanical strength. The degree of polymerization can be measured according to JIS K6726.

The weight average molecular weight of the water-soluble polymer is preferably 8,000 to 100,000, more preferably 8,000 to 45,000. The weight average molecular weight of the water-soluble polymer can be measured by gel permeation chromatography.

The melting point of the water-soluble polymer is preferably 150°C to 250°C, more preferably 160°C to 240°C, still more preferably 170°C to 230°C. Within such a range, a resin molding having excellent mechanical strength can be obtained.

In one embodiment, the melting point of the water-soluble polymer is higher than the melting point of the thermoplastic resin. The melting point of the water-soluble polymer is preferably 5° C. or higher, more preferably 10° C. or higher, and still more preferably 25° C. or higher, than the melting point of the thermoplastic resin.

As mentioned above, the water-soluble polymer is preferably fibrous. Since the water-soluble polymer is fibrous, a resin molding having excellent mechanical strength can be obtained. The fiber diameter (number average diameter) of the water-soluble polymer is preferably 100 µm or less, more preferably 50 µm or less, and even more preferably 10 µm or less. The lower limit of the fiber diameter (number average diameter) of the water-soluble polymer is, for example, 0.1 μm. The fiber length (number average length) of the water-soluble polymer is preferably 50 μm or longer, more preferably 100 μm or longer, and still more preferably 200 μm or longer. The upper limit of the fiber length (number average length) of the water-soluble polymer is, for example, 2000 μm. The aspect ratio (fiber length/fiber diameter) of the water-soluble polymer is preferably 5 or more and 2000 or less, more preferably 8 or more and 1000 or less, and still more preferably 10 or more and 500 or less. By dispersing the water-soluble polymer having such a shape in the resin composition, it is possible to obtain a resin molded article having more excellent mechanical strength.

The content of the water-soluble polymer is preferably 1.5 parts by weight to 15 parts by weight, more preferably 3 parts by weight to 14 parts by weight, with respect to 100 parts by weight of the total amount of the polyolefin resin. It is preferably 5 to 12 parts by weight. Within such a range, a resin molding having particularly excellent mechanical strength can be obtained.

The resin composition may further contain any appropriate additive as necessary. Additives include, for example, flow modifiers, anti-damage agents, heat stabilizers, stabilizers such as weathering agents, colorants such as pigments and dyes, lubricants, cross-linking agents, cross-linking aids, anti-blocking agents, and antistatic agents. agents, antifogging agents, organic fillers, inorganic fillers, and the like.

A-2. Method for Producing Resin Composition The resin composition can be produced by any appropriate method. In one embodiment, the resin composition is prepared by dissolving a water-soluble polymer in a solvent to prepare a solution; It can be obtained by a production method including melt-kneading; and removing the solvent after melt-kneading. According to such a production method, it is possible to obtain a resin composition and a resin molding containing a water-soluble polymer dispersed in fibrous form. In the present specification, melt-kneading means kneading under conditions in which the thermoplastic resin is melted.

The concentration of the water-soluble polymer in the solution is preferably 5-50% by weight, more preferably 10-40% by weight, even more preferably 15-25% by weight. Within such a range, it is possible to obtain a resin composition composed of a preferably fiberized water-soluble polymer present with good dispersibility.

Any suitable solvent can be used as the solvent as long as it can dissolve the water-soluble polymer at a concentration of 1% by weight or more at 25°C. Examples of the solvent include water, alcohol, ethylene glycol, triethylene glycol, glycerin, acetamide, dimethylacetamide, dimethylsulfoxide and the like, and two or more solvents can be mixed and used. Among them, water is preferred.

The water-soluble polymer solution may further contain any appropriate additive as necessary. Examples of additives include dispersants, antifoaming agents, flow modifiers, surfactants, salts, organic fillers, inorganic fillers, and the like.

Examples of the melt-kneading method include a method using a kneading device such as a single-screw extruder, a multi-screw extruder, a tandem extruder, and a Banbury mixer.

In one embodiment, the melt-kneading is performed using a continuous melt-kneading device (for example, a twin-screw extruder).

In one embodiment, the solution and thermoplastic resin (polypropylene resin, polyolefin resin other than polypropylene resin) are separately charged into a kneading device. Preferably, a thermoplastic resin (polypropylene resin, polyolefin resin other than polypropylene resin) is melted, and then the solution is added to the resin, and the solution and the resin are put into a kneading device. be. For example, a continuous type comprising a main throat that is a material input port, a discharge port that discharges the resin composition obtained after kneading, and a side feeder (liquid addition nozzle) provided between the main throw and the discharge port. Using the melt-kneading apparatus of No. 1, the thermoplastic resin is charged from the main throat, and after the thermoplastic resin is melted, the solution is charged from the side feeder. In one embodiment, the solution is added by injecting the solution at a pressure higher than the internal pressure of the melt-kneading device.

Any appropriate processing conditions for melt-kneading can be adopted as long as the effects of the present invention can be obtained.

The melting temperature during melt-kneading is preferably 160°C to 230°C, more preferably 180°C to 210°C.

The screw rotation speed during melt-kneading is preferably 50 rpm to 500 rpm, more preferably 100 rpm to 300 rpm. Within such a range, the water-soluble polymer can be fiberized particularly preferably.

Solvent removal after melt-kneading can be performed by any appropriate method. In one embodiment, a continuous melt-kneading apparatus is provided with a vacuum vent, and the pressure inside the melt-kneading apparatus is reduced by the vacuum vent, thereby removing the solvent from the melt-kneaded mixture containing the solution and the thermoplastic resin. Remove.

In another embodiment, a water-soluble polymer (e.g., powdery water-soluble polymer) and a thermoplastic resin (polypropylene resin, polyolefin resin other than polypropylene resin) are melt-kneaded and extruded to obtain pellets. The above resin composition can be obtained by giving a sufficient flow rate (shear rate) at the exit of the die. A resin composition containing a water-soluble polymer dispersed in fibrous form can also be obtained by such a production method.

Preferably, the mixture of the water-soluble polymer and the thermoplastic resin (mixture after melt-kneading) is extruded at a shear rate of 100 sec ⁻¹ or more. The shear rate is more preferably 1000 sec ^-1 or higher. The upper limit of the shear rate of the resin composition during melt molding is, for example, 10000 sec ⁻¹ . Within such a range, as described above, the orientation of the water-soluble polymer is enhanced, and a resin composition capable of forming a resin molded article having superior mechanical strength can be obtained.

In one embodiment, the resin composition is provided in the form of pellets. Pelletization of the resin composition can be performed by any suitable method.

B. Resin Molded Article By melt-molding the resin composition, films, fibers and other resin molded articles having various shapes can be obtained. Melt molding methods include, for example, injection molding, extrusion molding (sheet molding, film molding) and blow molding. Among them, injection molding or extrusion molding is preferred.

At the time of melt-molding, the flow rate of the molten resin composition is preferably high within a range in which a resin molded article having desired characteristics can be molded. For example, by giving a sufficient flow rate (shear rate) at the exit of the die and inside the mold during the above-mentioned molding, the orientation of the water-soluble polymer is increased, and a resin molded product with excellent mechanical strength can be obtained. can. The shear rate of the resin composition during melt molding is preferably 100 sec ^-1 or higher, more preferably 1000 sec ^-1 or higher. The upper limit of the shear rate of the resin composition during melt molding is, for example, 10000 sec ⁻¹ . Within such a range, as described above, the orientation of the water-soluble polymer is high, and a resin molded article having more excellent mechanical strength can be obtained.

The melting temperature during melt molding is preferably a temperature at which the thermoplastic resin in the resin composition can be melted and a temperature at which the water-soluble polymer can maintain its fibrous state.

The resin molding can be molded into, for example, sheet-like, film-like, rod-like, tube-like, block-like, irregular shape, and the like, depending on the application. Examples of the form of the molded article include containers, freezer bags, blown bottles, trays, packaging materials, tapes, and lid materials. Moreover, the said molded object can also be used as a covering material. The resin molded article of the present invention is particularly effective in the form of sheet, film, etc., because it has low density but excellent mechanical properties and can maintain a predetermined shape even though it is a thin film. Therefore, the resin molded article of the present invention can be particularly preferably used for packaging materials and the like.

A sheet-like molded article and a film-like molded article can be produced by, for example, a T-die casting method, an inflation molding method, or the like. A sheet-shaped molded article and a film-shaped molded article can be molded, for example, by charging the resin composition into a single-screw or twin-screw extruder, melt-kneading it with a screw, and extruding it from a die such as a T-die. In the case of T-die casting, a molten sheet of resin composition extruded from a T-die is cooled and solidified by contact with a roll to produce a sheet or film. In the case of a sheet-shaped molded body, the T-die casting molding method is preferable because of its high production stability. Moreover, it is good also as a multilayer structure containing one or more layers which consist of the resin composition of this invention. In the case of a multilayer structure, a co-extrusion method in which the thermoplastic resin other than the resin composition of the present invention extruded from another extruder during extrusion molding is extruded from a die, or a molded body pre-molded on a sheet or film. A (dry) lamination method is adopted in which the are laminated together with an adhesive or the like. A tray-shaped compact may be obtained by vacuum forming. As a method of vacuum molding, for example, after heating the sheet from the top and/or bottom for about 5 to 20 seconds with a heater adjusted to a heater temperature of about 350 ° C. to 500 ° C., the mold surface of the tray is evacuated. Thus, there is a molding method in which the material is brought into close contact with the mold surface and shaped into the shape of the mold. Before the tray is brought into close contact with the mold surface, a method may be adopted in which the vicinity of the center of the tray is pushed from the opposite side of the mold with a projection called a plug, and then brought into close contact with the mold.

The resin molding preferably has a specific gravity of 1 or less, more preferably less than 1, and still more preferably 0.9 to 0.99. Such a low-density resin molded product is advantageous in that it can be made lighter, and is also advantageous in that it can be easily separated from molded products made of other materials at the time of recycling.

EXAMPLES The present invention will be specifically described below with reference to Examples, but the present invention is not limited to these Examples. Evaluation methods in the examples are as follows. Parts and percentages are based on weight unless otherwise specified.

(1) Tensile modulus (extruded sheet-like molded body)
The tensile modulus of elasticity of the extruded sheet-like molded product was measured according to JIS K 7127.
The test piece was made into the strip shape of 25 mm width x 120 mm. The measurement temperature was 23° C., and the tensile speed was 1 mm/min. The tensile modulus was measured in each of the machine direction (MD) and the width direction (TD) during sheet production, with the longitudinal direction of the test piece as the tensile direction.

(2) Tensile modulus (resin molding by injection molding)
Based on JIS K 7161, the sample thickness was 4.0 mm, the test speed was 1.0 mm/min, and the measurement was performed at 23°C. The tensile direction was parallel to the injection direction of the resin composition.

(3) Flexural modulus Measured according to JIS K 7171 at a sample thickness of 4.0 mm, a test speed of 2.0 mm/min, and 23°C.

(4) DuPont Impact Test A DuPont impact test was performed according to JIS C5600-5-3, and the 50% impact fracture energy was determined according to JIS K7211-1. It means that the higher the fracture energy, the better the low-temperature impact resistance.

(5) Vacuum forming and buckling strength of the vacuum formed product The sheet formed product is pasted back from above and below with an infrared heater adjusted to 470 degrees at the central portion of the sheet formed product held in the vacuum forming machine. After heating for 18 seconds, the plug and the mold were brought into contact in that order, the sheet molding was sucked from the mold, and the shape of the mold was shaped to produce a tray-shaped molding. The temperature of the sheet molded body after heating was 170 degrees. The mold used this time had a tray shape with four pockets of 45 mm×90 mm×20 mm deep.
Buckling strength was measured in compression mode using a tensile test. Cut off one pocket from a tray molded body consisting of four pockets, place it on a plate installed perpendicular to the operating direction of the tensile tester (parallel to the ground) with the depression facing downward, and measure the diameter attached to the tip of the load cell A stainless plate of 22 mm and a thickness of 20 mm was used for compression at a compression speed of 30 mm/min, and the load at which the side walls of the tray molded body buckled was determined. (Buckling occurred at a compression width of about 10 mm for a tray molded product with a depth of 20 mm). The buckling strength (N/mm) was obtained by dividing this load by the thickness (mm) of the thinnest portion of the side wall, which was obtained in advance using a thickness gauge.

(6) Appearance Evaluation The appearance (color) of the tray molded product obtained in (5) above was visually confirmed.

(7) Fiber Length and Fiber Diameter of Water-Soluble Polymer Using a microtome, a 20 μm-thick thin film was collected from an extruded sheet-shaped article and an injection-molded resin article, and immersed in hot water at 90° C. for 4 hours. A sample for observation was prepared by completely dissolving and removing the water-soluble polymer from the flake. That is, since the water-soluble polymer was present in the voids in the thin section after immersion, the sample was observed with an optical microscope (300x), and the length and width of 20 arbitrary voids were measured. , and the average value was taken as the fiber length and the fiber diameter.

[Example 1]
(Formation of resin composition)
A twin-screw extruder (manufactured by Toshiba Machine, trade name “TEM37SS”), polypropylene (manufactured by Sumitomo Chemical Co., Ltd., trade name “Noblen AH1311”, melting point: 164 ° C., block copolymer) 72 parts by weight, linear 18 parts by weight of low-density polyethylene (manufactured by Prime Polymer Co., Ltd., trade name “Evolue SP3010”, melt flow rate: 0.8 g/10 min (190° C., 2.16 kgf), density: 926 kg/m ³ ), and a water-soluble polymer 10 parts by weight of P1 (polyvinyl alcohol, manufactured by Kuraray Co., Ltd., product name "PVA-103", completely saponified, degree of polymerization: 300, melting point: 221°C) was added, heated to 200°C, and these resins ( Polyolefin resin) was brought into a molten state, moisture generated from a vacuum vent was removed, extruded into a filament from a strand die, cooled in a water tank, and cut with a pelletizer to produce resin composition pellets.
(extrusion molding)
After drying the resin composition pellets at 90 ° C. for 10 hours in a dehumidifying dryer, they are put into a φ50 mm extruder adjusted to 200 ° C., melted and kneaded, and extruded from a T die with a width of 300 mm to form a sheet with a thickness of 0.5 mm. It was wound up at a line speed of 1.5 m/min to produce a sheet-shaped compact.
The obtained sheet-shaped molding was subjected to the above evaluation. Results are shown in Tables 1 and 2.

[Example 2]
Water-soluble polymer P1 (polyvinyl alcohol, manufactured by Kuraray Co., Ltd., trade name “PVA-103”, complete saponification, degree of polymerization: 300, melting point: 221 ° C.) was replaced with water-soluble polymer P2 (polyvinyl alcohol, Mitsubishi Chemical Co., Ltd. A sheet-like molding was produced in the same manner as in Example 1, except that the product name "Nichigo G Polymer AZF8035Q", completely saponified, degree of polymerization: 300, melting point: 172° C.) was used. The obtained sheet-shaped molding was subjected to the same evaluation as in Example 1. Results are shown in Tables 1 and 2.

[Example 3]
A sheet-shaped molding was produced in the same manner as in Example 2, except that the amount of the water-soluble polymer P2 was changed to 5 parts by weight. The obtained sheet-shaped molding was subjected to the same evaluation as in Example 1. Results are shown in Tables 1 and 2.

[Comparative Example 1]
A resin molded product was obtained in the same manner as in Example 1, except that the blending amount of polypropylene was 80 parts by weight, the blending amount of polyethylene was 20 parts by weight, and no water-soluble polymer was added. The obtained sheet-shaped molding was subjected to the same evaluation as in Example 1. Results are shown in Tables 1 and 2.

[Example 4]
Instead of 72 parts by weight of polypropylene (trade name “Noblen AH1311” manufactured by Sumitomo Chemical Co., Ltd.), 98 parts by weight of polypropylene (trade name “Novatec PP MA1B” manufactured by Japan Polypropylene Co., Ltd., melting point: 167 ° C., homopolymer) was used. , water-soluble polymer P1 (polyvinyl alcohol, manufactured by Kuraray Co., Ltd., product name "PVA-103", completely saponified, degree of polymerization: 300, melting point: 221 ° C.) instead of 10 parts by weight, water-soluble polymer P2 (polyvinyl alcohol , Mitsubishi Chemical Corporation, trade name "Nichigo G Polymer AZF8035Q", fully saponified, degree of polymerization: 300, melting point: 172 ° C.) 2 parts by weight in the same manner as in Example 1, except that the resin composition A pellet was produced.
(injection molding)
The resin composition pellets were molded at a molding temperature of 185° C. with an injection molding machine (trade name “SI-80IV-D150B” 80 tons, manufactured by Toyo Machinery & Metal Co., Ltd.) to obtain a resin molding having a thickness of 4.0 mm.
The obtained resin molding was subjected to the above evaluation. Table 3 shows the results.

[Example 5]
A resin molding was obtained in the same manner as in Example 4, except that the blending amount of polypropylene was 95 parts by weight and the blending amount of water-soluble polymer P2 was 5 parts by weight.
The obtained resin molding was subjected to the same evaluation as in Example 4. Table 3 shows the results.

[Example 6]
A resin molding was obtained in the same manner as in Example 4, except that the blending amount of polypropylene was 90 parts by weight and the blending amount of water-soluble polymer P2 was 10 parts by weight.
The obtained resin molding was subjected to the same evaluation as in Example 4. Table 3 shows the results.

[Comparative Example 2]
A resin molding was obtained in the same manner as in Example 4, except that the water-soluble polymer P2 was not blended.
The obtained resin molding was subjected to the same evaluation as in Example 4. Table 3 shows the results.

The molded article of the present invention can be suitably used for containers, freezer bags, blown bottles, trays, packaging materials, tapes, lid materials, automobile parts and the like.

Claims (7)

A resin molding formed from a resin composition containing a polypropylene-based resin and a water-soluble polymer.
The resin molding according to any one of claims 1 to 6, wherein the water-soluble polymer is a polyvinyl alcohol-based resin. 2. The resin molding according to claim 1, wherein the polyvinyl alcohol resin has a degree of polymerization of 200 to 2,500. 3. The resin molding according to claim 1, wherein the polyvinyl alcohol-based resin has a saponification degree of 80 mol % or more. The resin molding according to any one of claims 1 to 3, wherein the water-soluble polymer is fibrous. 5. The molded resin article according to claim 1, wherein the content of said water-soluble polymer is 1.5 parts by weight to 15 parts by weight with respect to 100 parts by weight of the total polyolefin resin. The resin molding according to any one of claims 1 to 5, wherein the resin composition is a resin composition obtained by melt-kneading a polypropylene-based resin and a water-soluble polymer. The resin molding according to any one of claims 1 to 6, which has a specific gravity of 1 or less.