Method for manufacturing screw cap

Abstract

To provide a method for manufacturing a screw cap that exhibits a predetermined required performance while using a waste container material, which is a defective product excluded in a container manufacturing process.SOLUTION: There is provided a method for manufacturing a screw cap, the method including: injection molding a resin composition containing (A) polypropylene and (B) a waste container material containing (b1) polyethylene and (b2) an ethylene-vinyl alcohol copolymer, in which a content of (B) the waste container material in the resin composition is 5.0 pts.mass or more and 20.0 pts.mass or less based on 100 pts.mass of the resin composition.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a screw cap.

Background Art

[0002] For container bodies and caps of foods, drugs, etc., containers mainly composed of synthetic resins are often used.

[0003] As the container body, for example, blow bottles, blow tubes, etc. are known. Blow bottles, blow tubes, etc. have a plurality of layers with different functions laminated thereon, and it is easy to exhibit container characteristics according to the contents, and they can be manufactured at high efficiency and low cost by blow molding, so they are widely used as containers for beverages, seasonings, cosmetics, etc.

[0004] On the other hand, as a material for the cap, for example, it is known to use a resin composition containing polyolefin. For example, Patent Document 1 describes manufacturing a container cap using a resin composition containing polypropylene excellent in thermoplasticity and ethylene-vinyl alcohol copolymer excellent in gas barrier properties.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] When molding a synthetic resin or its composition into the shape of a container body, defects such as uneven wall thickness, burrs, air bubbles, cracks, foreign matters, etc. may occur. Containers in which such inconveniences occur are excluded as defective products in the product inspection of the containers.

[0007] Defective products that are rejected during container manufacturing are not shipped as products. Defective products are either sold cheaply to recyclers (recycling businesses) or treated as waste containers that are disposed of for a fee. In particular, multi-layer containers are made of multiple layers of materials with different functions, and it is difficult to separate each layer, so it is not easy to mix them with virgin materials and use them.

[0008] In addition, since the cap material is required to have the mechanical and chemical properties required for a container cap, there is a concern that blending recycled materials may impair the required performance of the cap.

[0009] On the other hand, known types of caps include hinge caps, screw caps, bayonet caps, etc. Of these, screw caps are suitable for portable containers.

[0010] The present invention has been made in consideration of the above circumstances. An object of the present invention is to provide a method for manufacturing a screw cap that exhibits a predetermined required performance while using waste container materials that are defective products rejected during container manufacturing. [Means for solving the problem]

[0011] The present invention is as follows. Aspect 1: (A) polypropylene, (B) (b1) waste container materials containing polyethylene and (b2) ethylene-vinyl alcohol copolymer; and injection molding a resin composition comprising: The content ratio of the (B) container waste material in the resin composition is 5.0 parts by mass or more and 20.0 parts by mass or less per 100 parts by mass of the resin composition. How screw caps are manufactured. Aspect 2: The manufacturing method according to aspect 1, wherein the (B) waste container material further contains (b3) acid-modified polyethylene. 《Aspect 3》The content ratio of the (b1) polyethylene in the (B) container waste material is 80.0% by mass or more and 97.0% by mass or less based on the total mass of the (B) container waste material, the content ratio of the (b2) ethylene-vinyl alcohol copolymer in the (B) container waste material is 3.0% by mass or more and 20% by mass or less based on the total mass of the (B) container waste material, The production method according to Aspect 1. 《Aspect 4》The content ratio of the (b1) polyethylene in the (B) container waste material is 80.0% by mass or more and 97.0% by mass or less based on the total mass of the (B) container waste material, the content ratio of the (b2) ethylene-vinyl alcohol copolymer in the (B) container waste material is 3.0% by mass or more and 20% by mass or less based on the total mass of the (B) container waste material, the mass ratio of the (b3) acid-modified polyethylene in the (B) container waste material is 0.3% by mass or more and 5.0% by mass or less based on the total mass of the (B) container waste material, The production method according to Aspect 2. 《Aspect 5》The production method according to any one of Aspects 1 to 4, wherein the (A) polypropylene is a random copolymer type polypropylene. 《Aspect 6》(A) Polypropylene and, (B) A container waste material containing (b1) polyethylene and (b2) ethylene-vinyl alcohol copolymer and composed of a resin composition containing, the content ratio of the (B) container waste material in the resin composition is 5.0 parts by mass or more and 20.0 parts by mass or less with respect to 100 parts by mass of the resin composition, Screw cap. 《Aspect 7》The screw cap according to Aspect 6, wherein the (B) container waste material further contains (b3) acid-modified polyethylene. 《Aspect 8》The content ratio of the (b1) polyethylene in the (B) container waste material is 80.0% by mass or more and 97.0% by mass or less based on the total mass of the (B) container waste material, The content ratio of the (b2) ethylene-vinyl alcohol copolymer in the (B) container waste material is 3.0 parts by mass or more and 20% by mass or less based on the total mass of the (B) container waste material. The screw cap according to aspect 6. <<Aspect 9>> The content ratio of the (b1) polyethylene in the (B) container waste material is 80.0% by mass or more and 97.0% by mass or less based on the total mass of the (B) container waste material. The content ratio of the (b2) ethylene-vinyl alcohol copolymer in the (B) container waste material is 3.0 parts by mass or more and 20% by mass or less based on the total mass of the (B) container waste material. The mass ratio of the (b3) acid-modified polyethylene in the (B) container waste material is 0.3% by mass or more and 5.0% by mass or less based on the total mass of the (B) container waste material. The screw cap according to aspect 7. <<Aspect 10>> 80.0% by mass or more and 95.0% by mass or less of (A) polypropylene 4.0% by mass or more and 19.5% by mass or less of (b1) polyethylene 0.15% by mass or more and 4.0% by mass or less of (b2) ethylene-vinyl alcohol copolymer A screw cap made of a resin composition containing the above. <<Aspect 11>> The screw cap according to aspect 10, wherein the resin composition further contains 1.0% by mass or less of (b3) acid-modified polyethylene. <<Aspect 12>> The screw cap according to any one of aspects 6 to 11, wherein the (A) polypropylene is a random copolymer type polypropylene.

Advantages of the Invention

[0012] According to the present invention, a manufacturing method of a screw cap showing predetermined required performance is provided while using container waste materials which are defective products excluded in container manufacturing.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

DETAILED DESCRIPTION OF THE INVENTION

[0014] 《Method for Manufacturing a Screw Cap》 According to a first aspect of the present invention, there is provided a method for manufacturing a screw cap.

[0015] The method for manufacturing a screw cap according to the first aspect of the present invention (A) polypropylene and (B) a container waste material containing (b1) polyethylene and (b2) an ethylene-vinyl alcohol copolymer including injection molding a resin composition containing the same, wherein the content ratio of the (B) container waste material in the resin composition is 5.0 parts by mass or more and 20.0 parts by mass or less with respect to 100 parts by mass of the resin composition, is a manufacturing method.

[0016] In the resin composition constituting the screw cap of the present invention, a container waste material containing (A) polypropylene (PP), (B) (b1) polyethylene (PE), and (b2) ethylene-vinyl alcohol copolymer (EVOH) is blended. This container waste material is a waste material of a container having a multilayer structure in which (A) polypropylene (PP), (B) (b1) polyethylene (PE), and (b2) ethylene-vinyl alcohol copolymer (EVOH) are laminated in layers. Therefore, the components in this container waste material are mixed. This container waste material may further contain (b3) acid-modified polyethylene (PE-A) in addition to (b1) polyethylene (PE) and (b2) ethylene-vinyl alcohol copolymer (EVOH).

[0017] Container waste materials often have layers of a plurality of materials with different functions laminated thereon. Therefore, when blending the container waste material with PP, there is a concern that the original function of PP may be impaired. However, in the present invention, by selecting a container waste material containing specific components and adjusting the blending amount thereof, the obtained screw cap has the original dimensional accuracy of PP, good appearance, etc.

[0018] Hereinafter, the components contained in the resin composition used in the manufacturing method of the screw cap of the present invention will be described in order.

[0019] 〈(A) Polypropylene (PP)〉 (A) PP may be a homopolymer of propylene or a copolymer of propylene and other monomers. As the other monomers, olefins other than propylene can be preferably used. Specifically, for example, α-olefins having 2 or 4 to 10 carbon atoms can be exemplified, and preferably ethylene, 1-butene, 1-pentene, or 1-hexene.

[0020] When (A)PP is a copolymer of propylene and other monomers, the copolymerization form may be any of block copolymers, random copolymers, and mixtures thereof. Also, mixtures of propylene homopolymers and copolymers of propylene and other monomers are acceptable.

[0021] The crystal structure of the PP portion may be any of isotactic, syndiotactic, and atactic.

[0022] (A)PP used in the present invention may be a random copolymer type of polypropylene. The random copolymer type of polypropylene is suitable in that it has high transparency, so that the degree of freedom in the color of the cap is high and a cap with excellent design can be obtained.

[0023] (A)PP used in the present invention may be, for example, a random copolymer of propylene and ethylene. Particularly preferably, it is a random copolymer of propylene and ethylene, and the crystal structure of the PP portion is isotactic.

[0024] (A)PP used in the present invention may have a relatively high MFR in order to ensure molding accuracy. For example, in accordance with JIS K 6921-2, the melt mass flow rate (MFR) measured at a temperature of 230 °C and a load of 2.16 kg may be 8.0 g / 10 min or more, 10.0 g / 10 min or more, 12.0 g / 10 min or more, 15.0 g / 10 min or more, 17.0 g / 10 min or more, or 20.0 g / 10 min or more. On the other hand, in order to ensure moldability and heat resistance, the above MFR may be 80.0 g / 10 min or less, 60.0 g / 10 min or less, 50.0 g / 10 min or less, 40.0 g / 10 min or less, 30.0 g / 10 min or less, or 20.0 g / 10 min or less.

[0025] The density of (A)PP may be about 890 kg / m3 or more and 910 kg / m3 or less, and the tensile modulus may be about 500 MPa or more and 1,000 MPa or less.

[0026] The above characteristics regarding (A) PP are the characteristics of the entire mixture when the (A) component is a mixture of two or more types of PP.

[0027] 〈(B) Container waste material〉 The container waste material of the (B) component contains (b1) polyethylene and (b2) ethylene-vinyl alcohol copolymer. This container waste material may further contain (b3) acid-modified polyethylene.

[0028] ((b1) Polyethylene (PE)) The polyethylene (PE) contained in the (B) container waste material used in the present invention may be a homopolymer of ethylene or a copolymer of ethylene and other olefins. PE may be any of low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and high-density polyethylene (HDPE).

[0029] The (b1) PE contained in the (B) container waste material used in the present invention may be LDPE. This LDPE may be polyethylene containing 80 mol% or more, 90 mol% or more, 95 mol% or more, or 98 mol% or more of repeating units of methylene groups including branched chains, or polyethylene in which substantially all repeating units are methylene groups.

[0030] The density of LDPE may be less than 0.930 g / cm 3 and may be less than 0.925 g / cm 3 or less, or may be less than 0.923 g / cm 3 or less, and may be 0.870 g / cm3 or more, 0.875 g / cm 3 or more, 0.880 g / cm 3 or more, 0.900 g / cm 3 or more, 0.910 g / cm 3 or more, or may be 0.915 g / cm 3 or more.

[0031] As for the thermal properties of LDPE, although not particularly limited, for example, when its melt mass flow rate is measured in accordance with JIS K6922-1 and -2, and JIS K7210-1 under the conditions of a temperature of 190 °C and a load of 21.18 N, it may be 0.05 g / 10 min or more, 0.1 g / 10 min or more, 0.2 g / 10 min or more, 0.3 g or more, or 0.4 g / 10 min or more, and may be 10 g / 10 min or less, 5.0 g / 10 min or less, 3.0 g / 10 min or less, or 1.0 g / 10 min or less.

[0032] ((b2) Ethylene-vinyl alcohol copolymer (EVOH)) The (B) EVOH used in the present invention is a copolymer of ethylene and vinyl alcohol. The copolymerization ratio of ethylene in (b2) EVOH may be 20 mol% or more and 47 mol% or less, and may be 25 mol% or more and 32 mol% or less.

[0033] (b2) EVOH may be obtained, for example, by saponifying a copolymer of ethylene and vinyl carboxylate (e.g., vinyl acetate). In this case, the saponification degree of (B) EVOH may be 75 mol% or more, 80 mol% or more, 85 mol% or more, 90 mol% or more, or 95 mol% or more, or may be a completely saponified product with a saponification degree of 100 mol%. Here, the saponification degree refers to the ratio of the number of moles of vinyl alcohol units to the total number of moles of vinyl alcohol units and vinyl carboxylate units in (b2) EVOH.

[0034] (b2) For EVOH, the melt mass flow rate (MFR) measured in accordance with JIS K 6921-2 at a temperature of 190 °C and a load of 2.16 kg may be about 1.0 g / 10 min or more and 8.0 g / 10 min or less. The density of (b2) EVOH is 1,100 kg / m 3 or more and 1,200 kg / m 3 or less.

[0035] ((b3)) Acid-modified polyethylene (PE-A) The (b3) PE-A used in the present invention may be obtained by, for example, a method of graft-polymerizing an unsaturated carboxylic acid onto polyethylene (PE) which is a base resin. By including (b3) PE-A in the resin composition, it is considered that (A) polypropylene (PP), (B) (b1) polyethylene (PE), and (b2) ethylene-vinyl alcohol copolymer (EVOH) will mix better.

[0036] The PE as the base resin may be a homopolymer of ethylene or a copolymer of ethylene and other olefins.

[0037] The unsaturated carboxylic acid grafted onto the PE of the base resin may be, for example, one or more selected from unsaturated carboxylic acids such as acrylic acid, maleic acid, fumaric acid, tetrahydrophthalic acid, itaconic acid, crotonic acid, citraconic acid, and acid anhydrides thereof.

[0038] The graft ratio of the unsaturated carboxylic acid in (b3) PE-A may be evaluated by oxidation measured in accordance with JIS K 0070. This oxidation is the number of milligrams (mg) of potassium hydroxide required to neutralize the acid groups and acid anhydride groups in 1 g of (b3) PE-A. The acid value of (b3) PE-A may be, for example, about 0.15 or more and 10 or less.

[0039] For (b3) PE-A, the melt mass flow rate (MFR) measured at a temperature of 190 °C and a load of 2.12 N in accordance with JIS K 6921-2 may be about 1.0 g / 10 min or more and 30 g / 10 min or less. The density of (b3) PE-A is 0.925 g / cm 3 or more and 0.935 g / cm 3 or less.

[0040] 〈Optional component〉 In addition to the above-mentioned (A) PP and (B) container waste materials, the resin composition used in the present invention may contain optional components. The optional components may be, for example, one or more selected from dyes, antioxidants, antistatic agents, thickeners, defoamers, surface modifiers, fillers, etc.

[0041] ((Content ratio of each component in (B) container waste material)) (The content ratio of (b1) PE in (B) container waste material may be 80.0% by mass or more, 82.5% by mass or more, 85.0% by mass or more, or 90.0% by mass or more, and may be 97.0% by mass or less, 95.0% by mass or less, 93.0% by mass or less, or 92.0% by mass or less, based on the total mass of (B) container waste material.

[0042] (The content ratio of (b2) EVOH in (B) container waste material may be 3.0 parts by mass or more, 5.0 parts by mass or more, 6.0 parts by mass or more, 7.0 parts by mass or more, or 8.0 parts by mass or more, and may be 20% by mass or less, 18% by mass or less, 16% by mass or less, 14% by mass or less, 12% by mass or less, 10% by mass or less, or 9.0% by mass or less, based on the total mass of the (B) container waste material.

[0043] When (B) container waste material contains (b3) PE - A, its content ratio may be 0.3% by mass or more, 0.5% by mass or more, 0.7% by mass or more, 1.0% by mass or more, or 1.2% by mass or more, and may be 5.0% by mass or less, 4.0% by mass or less, 3.0% by mass or less, 2.0% by mass or less, or 1.5% by mass or less, based on the total mass of (B) container waste material.

[0044] In the present invention, by using a predetermined amount of (B) container waste material containing each component in the above ratio, the obtained cap has the original dimensional accuracy of (A) PP, good appearance, etc.

[0045] ((Origin of (B) container waste material)) (B) The container waste material used in the present invention may be waste material of any container as long as it has the above composition. The (B) container waste material used in the present invention may be, for example, a blow bottle, a blow tube, etc. having a PE layer, an EVOH layer, and an adhesive layer (PE-A layer).

[0046] When the (B) container waste material is waste material of a food container, the materials contained in the container waste material are likely to be materials listed in the "Positive List" determined by, for example, the Sanitary Council such as polyolefin. Therefore, when the resin composition in the present invention contains such container waste material, there is an advantage that it becomes easy to apply the obtained cap to food use.

[0047] (Content ratio of (B) container waste material in the resin composition) The content ratio of the (B) container waste material in the resin composition used in the present invention is 5.0 parts by mass or more and 20.0 parts by mass or less with respect to 100 parts by mass of the resin composition.

[0048] If the content ratio of the (B) container waste material with respect to 100 parts by mass of the resin composition is 5.0 parts by mass or more, container waste recycling becomes effective. From this viewpoint, the content ratio of the (B) container waste material in the resin composition may be 5.0 parts by mass or more, 7.5 parts by mass or more, 10.0 parts by mass or more, 12.5 parts by mass or more, or 15.0 parts by mass or more with respect to 100 parts by mass of the resin composition.

[0049] On the other hand, if this ratio is 20.0 parts by mass or less, the properties that (A) PP originally has are hardly impaired even by the blending of the container waste material. From this viewpoint, the content ratio of the (B) container waste material in the resin composition may be 20.0 parts by mass or less, 17.5 parts by mass or less, 15.0 parts by mass or less, 12.5 parts by mass or less, or 10.0 parts by mass or less with respect to 100 parts by mass of the resin composition. In addition, when the content ratio of the (B) container waste material in the resin composition is 15.0 parts by mass or less, 12.5 parts by mass or less, or 10.0 parts by mass or less with respect to 100 parts by mass of the resin composition, in addition to the fact that the properties of (A) PP are hardly impaired, there is also an advantage that the impact resistance of the obtained cap is improved.

[0050] (Injection molding) In the present invention, the injection molding for forming the cap from the above resin composition may be carried out by a known method or a method obtained by arbitrarily modifying this by those skilled in the art. Specifically, general conditions for injection molding of polypropylene resin may be adopted. For example, it may be injection molding at a temperature of 180°C or higher and 280°C or lower, or 200°C or higher and 250°C or lower.

[0051] (The screw cap to be manufactured) Hereinafter, an example of the structure of the screw cap manufactured by the method of the present invention will be described with reference to the drawings. However, the screw cap manufactured by the method of the present invention is not limited thereto.

[0052] FIG. 1 shows a schematic diagram for explaining an example of the structure of the screw cap manufactured by the method of the present invention. FIG. 1(a) is a bottom view, and FIG. 1(b) is a cross-sectional view taken along line A-A of FIG. 1(a).

[0053] The screw cap (100) in FIG. 1 has a base (110), a peripheral wall (120), and an outer wall (130). On the inner surface of the peripheral wall (120), there is a cap thread (121) for screwing with the mouth of the container body. On the other hand, the outer wall (130) does not have a threaded portion. Further, the screw cap (100) has an outer ring (111) and an inner pin (112) that project from the back surface side of the base (110) in order to fit with the mouth of the container body and form a seal.

[0054] The screw cap (100) has a cap engaging convex portion (122) at the tip of the peripheral wall (120) (the position farthest from the base (110)). The cap engaging convex portion (122) is a convex portion that projects radially outward of the screw cap (100) at two positions on the outer surface of the tip of the peripheral wall (120) that are opposed in the radial direction.

[0055] Fig. 2 shows a schematic diagram for explaining an example of the structure near the mouth of a container body that is used in screwing engagement with a screw cap manufactured by the method of the present invention. Fig. 2(a) is a top view of the container body, and Fig. 2(b) is a right side view of the upper part of the container body.

[0056] Fig. 2 shows the vicinity of the container mouth portion (210) and the shoulder portion (220) of the container body (200).

[0057] The container mouth portion (210) shown in Fig. 2 has a lip portion (211) and a container mouth portion thread (212) that is protruded on the outer surface of the neck portion and is screwed with the cap thread (121) of the screw cap (100).

[0058] Further, the container body (200) has a pair of container mouth portion protrusions (213a, 213b) near the boundary between the container mouth portion (210) and the shoulder portion (220), and the gap between these pair of protrusions constitutes a container mouth portion engaging recess (214). The container mouth portion protrusions (213a, 213b) exist in pairs at two locations facing each other in the radial direction of the container mouth portion (210). Therefore, the container mouth portion engaging recesses (214) are formed at two locations facing each other in the radial direction of the container mouth portion (210).

[0059] When the screw cap (100) is tightened to the container mouth portion (210), the cap engaging convex portion (122) of the screw cap (100) engages with the container mouth portion engaging recess (214) of the container mouth portion (210) and functions as a locking mechanism. When the screw cap and the container mouth portion have a locking mechanism, the cap assembly including the screw cap of the present invention is easy to close and difficult to loosen.

[0060] 《Screw Cap》 According to a second aspect of the present invention, (A) Polypropylene, and (B) A container waste material containing (b1) polyethylene and (b2) an ethylene-vinyl alcohol copolymer, and composed of a resin composition containing The content ratio of (B) waste container materials in the resin composition is 5.0 parts by mass or more and 20.0 parts by mass or less with respect to 100 parts by mass of the resin composition. A screw cap is provided.

[0061] The screw cap according to the second aspect of the present invention may be manufactured, for example, by the method for manufacturing the screw cap of the present invention described above. Therefore, regarding the details of the resin composition constituting the screw cap according to the second aspect of the present invention, the description of the resin composition in the method for manufacturing the screw cap of the present invention may be applied as it is.

[0062] Therefore, the (B) waste container material may further contain (b3) acid-modified polyethylene.

[0063] Also, the content ratio of (b1) polyethylene in the (B) waste container material may be 80.0% by mass or more and 97.0% by mass or less based on the total mass of the (B) waste container material. The content ratio of (b2) ethylene-vinyl alcohol copolymer in the (B) waste container material may be 3.0 parts by mass or more and 20% by mass or less based on the total mass of the (B) waste container material. The mass ratio of (b3) acid-modified polyethylene in the (B) waste container material may be 0.3% by mass or more and 5.0% by mass or less based on the total mass of the (B) waste container material. Regarding the preferred content ratios of these components, the description of the resin composition in the method for manufacturing the screw cap of the present invention may be applied as it is.

[0064] According to the third aspect of the present invention, (A) Polypropylene 80.0% by mass or more and 95.0% by mass or less, (b1) Polyethylene 4.0% by mass or more and 19.5% by mass or less, (b2) Ethylene-vinyl alcohol copolymer 0.15% by mass or more and 4.0% by mass or less A screw cap made of a resin composition containing the above is provided.

[0065] The resin composition constituting the screw cap according to the third aspect of the present invention may further contain 1.0% by mass or less of (b3) acid-modified polyethylene.

[0066] The screw cap according to the third aspect of the present invention may be manufactured, for example, by the method for manufacturing the screw cap of the present invention described above. Therefore, the description of each component in the resin composition in the method for manufacturing the screw cap of the present invention may be directly applied to each component in the resin composition constituting the screw cap according to the third aspect of the present invention.

[0067] The content ratios of the respective components of the resin composition constituting the screw cap according to the third aspect of the present invention may be as follows, respectively.

[0068] The content ratio of (A) polypropylene in the resin composition is 80.0% by mass or more, and may be 82.5% by mass or more, 85.0% by mass or more, 87.5% by mass or more, or 90.0% by mass or more. The content ratio of (A) polypropylene in the resin composition is 95.0% by mass or less, and may be 92.5% by mass or less, 90.0% by mass or less, 87.5% by mass or less, or 85.0% by mass or less.

[0069] The content ratio of (b1) polyethylene in the resin composition is 4.0% by mass or more, and may be 6.0% by mass or more, 8.0% by mass or more, 10.0% by mass or more, 12.0% by mass or more, or 15.0% by mass or more. The content ratio of (b1) polyethylene in the resin composition is 19.5% by mass or less, and may be 18.0% by mass or less, 15.0% by mass or less, 12.0% by mass or less, 10.0% by mass or less, 8.0% by mass or less, or 6.0% by mass or less.

[0070] The content ratio of the (b2) ethylene-vinyl alcohol copolymer in the resin composition is 0.15% by mass or more, and may be 0.5% by mass or more, 1.0% by mass or more, 2.0% by mass or more, or 3.0% by mass or more. The content ratio of the (b2) ethylene-vinyl alcohol copolymer in the resin composition is 4.0% by mass or less, and may be 3.5% by mass or less, 3.0% by mass or less, 2.5% by mass or less, 2.0% by mass or less, 1.5% by mass or less, or 1.0% by mass or less.

[0071] The resin composition may not contain the (b3) acid-modified polyethylene. When the resin composition contains the (b3) acid-modified polyethylene, the content ratio may be 0.05% by mass or more, 0.10% by mass or more, 0.20% by mass or more, 0.50% by mass or more, or 0.70% by mass or more. The content ratio of the (b3) acid-modified polyethylene in the resin composition is 1.0% by mass or less, and may be 0.80% by mass or less, 0.60% by mass or less, 0.50% by mass or less, 0.30% by mass or less, or 0.20% by mass or less.

Examples

[0072] 《Example 1》 (1) Manufacture of screw cap (B) As container waste materials, crushed materials obtained by crushing multilayer PE blow bottle waste materials to about 4 mm in diameter were used. These waste materials contained the following components (b1) to (b3) in the following ratios. (b1) component: LDPE (MFR 0.4 g / 10 min (JIS K 7210-1, 190 °C, 2.16 kg)) 90.00% by mass (b2) component: EVOH (ethylene copolymerization ratio: 32 mol%, MFR: 4.1 g / 10 min (JIS K 6921-2, 190 °C, 2.16 kg), density: 1,180 kg / m 3 ) 8.75% by mass (b3) component: maleic acid-modified PE (PE-A) 1.25% by mass

[0073] As the PP of component (A), 90% by mass of a random copolymer type PP (product name: "PM931V" (MFR: 25 g / 10 min (JIS K 6921-2, 230 °C, 2.16 kg), density: 900 kg / m 3 ), pellets) manufactured by Sun Aroma Co., Ltd., and 10% by mass of container waste material were dry blended, and the blend was put into an injection molding machine equipped with a mold for cap production, and kneading and injection molding were performed in the temperature range of 180 °C to 250 °C to produce a screw cap having the shape shown in Fig. 1.

[0074] On the other hand, a container body having a mouth portion with the shape shown in Fig. 1 was manufactured using HDPE as a material.

[0075] When the obtained screw cap was tightened on the container body, the cap engaging convex portion of the screw cap and the mouth engaging concave portion of the mouth portion of the container body were engaged to function as a locking mechanism.

[0076] The composition of the obtained screw cap was as follows. Component (A): PP, 90.0% by mass Component (b1): LDPE, 9.00% by mass Component (b2): EVOH, 0.875% by mass Component (b3): PE-A, 0.125% by mass

[0077] (2) Evaluation of the screw cap i) Difference in opening and closing strength The closing strength when the obtained screw cap was screwed onto the mouth portion of the tube container and the opening strength when the screw cap in the closed state was removed from the mouth portion of the tube container were measured by a torque meter, respectively. These closing strength and opening strength are the forces required when the locking portion of the screw cap overrides the locking portion of the tube container mouth when closing and opening the screw cap. When the difference between the opening strength and the closing strength is 2 N or more, the screw cap can be evaluated as being easy to close and difficult to loosen.

[0078] ii) Drop resistance The obtained screw cap was combined with a 270 mL tube container filled with 270 g of water and sealed. After cooling this water-filled container to 5°C, it was dropped onto a concrete floor from a height of 1 m in the direction with the screw cap on. The screw cap after dropping was visually observed to examine the cracking situation.

[0079] 《Example 2》 (A) PP and (B) waste container materials were mixed at a ratio of 80% by mass and 20% by mass, and otherwise in the same manner as in Example 1, a hinge cap was manufactured and evaluated.

[0080] The composition of the obtained cap was as follows. (A) component: PP, 80.0% by mass (b1) component: LDPE, 18.0% by mass (b2) component: EVOH, 1.75% by mass (b3) component: PE-A, 0.25% by mass

[0081] 《Reference Example 1》 (B) Waste container materials were not used, and only (A) PP was used. Otherwise, in the same manner as in Example 1, a hinge cap was manufactured and evaluated.

[0082] The above results are shown in Table 1.

[0083]

Table 1

[0084] Referring to Table 1, the following can be understood.

[0085] The screw cap of Comparative Example 1 with a composition of 100% by mass of (A) PP had a difference of 2 N between the opening strength and the closing strength and had the characteristics of being easy to close and difficult to loosen. However, the cap of Reference Example 1 was inferior in drop resistance, and cracks occurred due to dropping from a height of 1 m.

[0086] In contrast, the screw caps of Examples 1 and 2 containing a predetermined amount of (b1) LDPE, (b2) EVOH, and (b3) PE-A derived from container waste materials in addition to (A) PP showed a greater difference in opening and closing strength than the screw cap of Comparative Example 1 and were also excellent in drop resistance.

Explanation of Reference Numerals

[0087] 100 Screw cap 110 Base 111 Outer ring 112 Inner pin 120 Peripheral wall 121 Cap screw 122 Cap engaging convex portion 130 Outer wall 200 Container body 210 Container mouth 211 Lip portion 212 Container mouth screw 213a, 213b Container mouth protrusion 214 Container mouth engaging recess 220 Shoulder

Claims

1. (A) Polypropylene, and (B) A container waste material containing (b1) polyethylene and (b2) an ethylene-vinyl alcohol copolymer, and Injecting and molding a resin composition containing the same, The content ratio of the (B) container waste material in the resin composition is 5.0 parts by mass or more and 20.0 parts by mass or less with respect to 100 parts by mass of the resin composition. A method for manufacturing a screw cap.

2. The manufacturing method according to claim 1, wherein the (B) container waste material further contains (b3) acid-modified polyethylene.

3. The content ratio of the (b1) polyethylene in the (B) container waste material is 80.0% by mass or more and 97.0% by mass or less based on the total mass of the (B) container waste material, The content ratio of the (b2) ethylene-vinyl alcohol copolymer in the (B) container waste material is 3.0 parts by mass or more and 20% by mass or less based on the total mass of the (B) container waste material. The manufacturing method according to claim 1.

4. The content ratio of the (b1) polyethylene in the (B) container waste material is 80.0% by mass or more and 97.0% by mass or less based on the total mass of the (B) container waste material, The content ratio of the (b2) ethylene-vinyl alcohol copolymer in the (B) container waste material is 3.0 parts by mass or more and 20% by mass or less based on the total mass of the (B) container waste material. The mass ratio of the (b3) acid-modified polyethylene in the (B) container waste material is 0.3% by mass or more and 5.0% by mass or less based on the total mass of the (B) container waste material. The manufacturing method according to claim 2.

5. The manufacturing method according to any one of claims 1 to 4, wherein the (A) polypropylene is a random copolymer type polypropylene.

6. (A) Polypropylene, and (B)(b1) polyethylene and (b2) ethylene-vinyl alcohol copolymer-containing container waste material and consisting of a resin composition containing the content ratio of the (B) container waste material in the resin composition is 5.0 parts by mass or more and 20.0 parts by mass or less with respect to 100 parts by mass of the resin composition, Screw cap.

7. The screw cap according to claim 6, wherein the (B) container waste material further contains (b3) acid-modified polyethylene.

8. The content ratio of the (b1) polyethylene in the (B) container waste material is 80.0% by mass or more and 97.0% by mass or less based on the total mass of the (B) container waste material, The content ratio of the (b2) ethylene-vinyl alcohol copolymer in the (B) container waste material is 3.0 parts by mass or more and 20% by mass or less based on the total mass of the (B) container waste material, The screw cap according to claim 6.

9. The content ratio of the (b1) polyethylene in the (B) container waste material is 80.0% by mass or more and 97.0% by mass or less based on the total mass of the (B) container waste material, The content ratio of the (b2) ethylene-vinyl alcohol copolymer in the (B) container waste material is 3.0 parts by mass or more and 20% by mass or less based on the total mass of the (B) container waste material, The mass ratio of the (b3) acid-modified polyethylene in the (B) container waste material is 0.3% by mass or more and 5.0% by mass or less based on the total mass of the (B) container waste material, The screw cap according to claim 7.

10. (A) 80.0% by mass or more and 95.0% by mass or less of polypropylene, (b1) 4.0% by mass or more and 19.5% by mass or less of polyethylene, (b2) 0.15% by mass or more and 4.0% by mass or less of ethylene-vinyl alcohol copolymer A screw cap made of a resin composition containing

11. The screw cap according to claim 10, wherein the resin composition further contains 1.0% by mass or less of (b3) acid-modified polyethylene.

12. The screw cap according to any one of claims 6 to 11, wherein the (A) polypropylene is a random copolymer type polypropylene.

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