JP7591971B2 - Cap with slit valve and method for manufacturing cap with slit valve - Google Patents

Description

The present invention relates to a cap with a slit valve and a method for manufacturing a cap with a slit valve.

Caps with slit valves, which are equipped with slit-type valves (slit valves), are widely used as dispensers for containers that store viscous foods or seasonings such as ketchup, honey, and mayonnaise. Caps with slit valves usually have a configuration in which cross-shaped, radial, or other slits are formed in an elastically deformable film placed at the opening of the cap.

A container fitted with a cap with a slit valve retains its contents under normal pressure, but when the body of the container is pressurized to increase the internal pressure of the container, the slit in the slit valve is pushed open by the pressure of the contents, and the contents are ejected. When pressure is removed from the body of the container, the slit in the slit valve closes due to its elasticity, and the ejection of the contents stops. Therefore, a container fitted with a cap with a slit valve can improve the liquid drainage when the contents are ejected.

Silicone resin has traditionally been used as the material that makes up the slit valve because it has suitable elasticity and is unlikely to react with the contents. On the other hand, the cap is often made of polypropylene (PP).

As a result, when attempting to recycle polypropylene caps with silicone valves discarded by ordinary consumers, there was a risk that the silicone would become a foreign matter during the crushing, melting, and re-mixing processes, compromising the quality and appearance of the recycled product.

Patent Document 1 describes a spout with a slit valve that is made of a non-fluorinated elastomer, and styrene- or olefin-based thermoplastic elastomers are preferred because of their superior food hygiene properties.

JP 2018-177296 A

Recently, as part of efforts to address environmental issues, efforts to recycle materials have been progressing, but the compatibility between styrene-based elastomers and PP is not necessarily good, so it is not a good idea to simply crush and melt the integrally molded product.

In addition, when using olefin-based thermoplastic elastomers as the constituent material of slit valves, wrinkles and burrs can appear on the valve when forming the slits, which can cause problems with processability.

When polyethylene is used as the constituent material of the slit valve, it has good compatibility with the PP cap material, and is less likely to cause problems such as the generation of lumps during material recycling. However, when polyethylene is used alone, the slit valve becomes hard, which can make it difficult to dispense the contents.

The present invention has been made in view of the above background, and aims to provide a cap with a slit valve, which has excellent compatibility when melt-kneading the cap base and the slit valve, allows for material recycling, has excellent discharge properties for the contents, and has good slit processability for the valve, and a method for manufacturing the cap with a slit valve.

The present inventors conducted extensive research to solve the above problems. They discovered that the above problems could be solved by applying a slit valve made of a composition containing low-density polyethylene and an ethylene-hexene copolymer, which is a copolymer of a monomer mixture containing at least ethylene and hexene, to a cap base made of a resin mainly composed of polypropylene, and thus completed the present invention. That is, the present invention is as follows.

Aspect 1
A cap substrate;
a slit valve provided at an opening of the mouth of the cap base and having a slit that opens when the internal pressure of the container increases;
A cap with a slit valve, comprising:
The cap base is made of a resin mainly composed of polypropylene, and
The slit valve is a cap with a slit valve, which is composed of a composition including a low density polyethylene and an ethylene-hexene copolymer which is a copolymer of a monomer mixture including at least ethylene and hexene.
Aspect 2
A cap with a slit valve according to claim 1, wherein the ratio of the low-density polyethylene constituting the slit valve is 20 to 80 mass%, relative to 100 mass % of the total of the low-density polyethylene and the ethylene-hexene copolymer constituting the slit valve.
Aspect 3
The cap with a slit valve according to aspect 1 or 2, wherein the ethylene-hexene copolymer has a density of 0.90 g/cm3 ^or less and a tensile modulus of elasticity of 100 MPa or less.
Aspect 4
The cap with a slit valve according to any one of aspects 1 to 3, wherein the cap base includes a lid body connected via a hinge.
Aspect 5
A cap with a slit valve according to any one of Aspects 1 to 4, wherein the slit valve is assembled and fixed to the cap base.
Aspect 6
A method for producing the cap with a slit valve according to aspect 5, comprising the steps of:
molding the cap base and the fitting ring using a resin mainly composed of polypropylene;
A method for manufacturing a cap with a slit valve, comprising: molding the slit valve using a composition containing low-density polyethylene and an ethylene-hexene copolymer, which is a copolymer of a monomer mixture containing at least ethylene and hexene; and assembling and fixing the cap base and the slit valve with the fitting ring.

The present invention provides a cap with a slit valve and a method for manufacturing a cap with a slit valve that has excellent compatibility when melt-kneading the cap base and the slit valve, allows for material recycling, and has excellent discharge properties for the contents.

FIG. 2 is a perspective view of a cap with a slit valve according to one embodiment of the present invention. 2 is a front view of the cap with a slit valve of FIG. 1 with the lid closed, and a cross-sectional view taken along line AA thereof. FIG.

<Cap with slit valve>
The slit valve cap of the present invention is
A cap substrate;
a slit valve provided at an opening of a mouth portion of a cap base and having a slit that opens in response to an increase in internal pressure of the container,
The cap base is made of a resin mainly composed of polypropylene, and
The slit valve is a cap with a slit valve made of a composition including low density polyethylene and an ethylene-hexene copolymer which is a copolymer of a monomer mixture including at least ethylene and hexene.

The cap base may include a lid connected via a hinge. A cap with a slit valve may include, as required components, a cap base and a slit valve, and may include other parts as desired. Examples of other parts include a fitting ring for assembling and fixing the cap base and the slit valve.

The cap base and its constituent materials in the cap with slit valve of the present invention will be described below. Next, the configuration of the cap with slit valve will be described.

<Constituent materials of cap body>
The cap base in the slit valve cap of the present invention is composed of a resin mainly composed of polypropylene. The term "resin mainly composed of polypropylene" refers to a resin composed of only polypropylene or a resin composition containing polypropylene and other resins, and the polypropylene content in the resin composition is more than 50% by mass, 60% by mass or more, 70% by mass or more, 80% by mass or more, 85% by mass or more, 90% by mass or more, 95% by mass or more, 98% by mass or more, or 99% by mass or more.

The polypropylene constituting the cap substrate may be a homopolymer of propylene or a copolymer of propylene and another monomer. As the other monomer, an olefin other than propylene can be preferably used. Specifically, for example, an α-olefin having 2 or 4 to 10 carbon atoms can be exemplified, and preferably ethylene, 1-butene, 1-pentene, or 1-hexene. Not only one type of other monomer but also two or more types may be used.

When polypropylene is a copolymer of propylene and other monomers, the form of the copolymerization may be a block copolymer, a random copolymer, or a mixture of these.

The crystal structure of polypropylene may be isotactic, syndiotactic, or atactic.

The polypropylene constituting the cap substrate is preferably a random copolymer or block copolymer of propylene and ethylene, and the crystal structure of the polypropylene is isotactic.

When the cap base has a lid, the lid and other parts of the cap base may be made of the same material or different materials. However, from the viewpoint of being able to manufacture a cap base with a lid in one process, it is preferable that the lid and other parts of the cap base are made of the same material.

When the cap base is a resin composition containing polypropylene and other resins, the other resins are not particularly limited as long as they do not impair the effects of the present invention. For example, olefin-based resins or elastomers may be used, as they are less likely to cause compatibility problems during material recycling in which the slit valve and the cap are melt-kneaded together. Various additives may also be added depending on the application.

When the cap with slit valve of the present invention includes a fitting ring and the cap base and the slit valve are assembled and fixed by the fitting ring, the fitting ring may be made of the same material as the cap base, or may be made of a different material. However, from the viewpoint of material recycling, it is preferable that the cap base and the fitting ring are made of the same material.

<Materials of the slit valve>
The slit valve in the cap with slit valve of the present invention is composed of a composition containing low density polyethylene and an ethylene-hexene copolymer which is a copolymer of a monomer mixture containing at least ethylene and hexene. The slit valve only needs to contain low density polyethylene and ethylene-hexene copolymer as essential components, and may contain other components as long as the effects of the present invention are not impaired.

(Low density polyethylene)
The low density polyethylene (LDPE) constituting the slit valve in the slit valve cap of the present invention refers to 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 in which substantially all of the repeating units are methylene groups.

The density of the low density polyethylene may be less than 0.930 g/ ^cm3 , 0.925 g/cm3 or ^less , or 0.923 g/cm3 or ^less , or may be 0.870 g/ ^cm3 or more, 0.875 g/cm3 or ^more , 0.880 g/ ^cm3 or more, 0.900 g/cm3 or ^more , 0.910 g/cm3 or ^more , or 0.915 g/ ^cm3 or more.

The low-density polyethylene may be a so-called linear low-density polyethylene (LLDPE), or may have a long-chain or short-chain branched structure. The short-chain branched structure may be a branched structure derived from an α-olefin having 4 to 18, 4 to 10, or 4 to 8 carbon atoms, such as 1-butene, 1-hexene, 4-methylpentene-1, or 1-octene.

The thermal properties of the preferred low-density polyethylene are not particularly limited, but for example, when measured in accordance with JIS K6922-1 and -2 and JIS K7210-1 under conditions of a temperature of 190°C and a load of 21.18 N, the melt mass flow rate may be 0.1 g/10 min or more, 0.5 g/10 min or more, 1.0 g or more, 3.0 g/10 min or more, or 5.0 g/10 min or more, and may be 100 g/10 min or less, 50 g/10 min or less, 30 g/10 min or less, or 20 g/10 min or less.

(Composition of low density polyethylene and ethylene-hexene copolymer)
The proportion of the low-density polyethylene constituting the slit valve may be 20 to 80 mass % relative to 100 mass % of the total of the low-density polyethylene constituting the slit valve and an ethylene-hexene copolymer, which is a copolymer of a monomer mixture containing at least ethylene and hexene, described below.

If the proportion of low-density polyethylene is within the above range, a cap with a slit valve that has excellent properties for discharging the contents can be realized.

The proportion of low-density polyethylene constituting the slit valve may be 30% by mass or more, 40% by mass or more, 50% by mass or more, 60% by mass or more, 70% by mass or more, and may be 75% by mass or less, 70% by mass or less, 65% by mass or less, 60% by mass or less, 55% by mass or less, 50% by mass or less, based on 100% by mass of the total of the low-density polyethylene and ethylene-hexene copolymer constituting the slit valve.

(Ethylene-hexene copolymer)
The ethylene-hexene copolymer is a copolymer of a monomer mixture containing at least ethylene and hexene (e.g., 1-hexene). The ethylene-hexene copolymer may be a binary copolymer obtained by copolymerization of ethylene and hexene, or a multicomponent copolymer obtained by copolymerization of a monomer mixture containing other monomers in addition to ethylene and hexene. In the present invention, the ethylene-hexene copolymer is preferably a multicomponent copolymer obtained by copolymerization of a monomer mixture containing other monomers in addition to ethylene and hexene.

As the other monomer, an olefin other than ethylene and hexene can be preferably used. Specifically, for example, an α-olefin having 3 to 5 or 7 to 10 carbon atoms can be exemplified, and preferably propylene, 1-butene, 1-pentene, or 1-octene.

The copolymer form of the ethylene-hexene copolymer may be a block copolymer, a random copolymer, or a mixture thereof.

It is believed that ethylene-hexene copolymers have a certain proportion of tertiary carbon derived from hexene units in the polymer chain, which is believed to improve compatibility during melt mixing with polypropylene, which also has many tertiary carbons in the polymer chain.

Therefore, it is presumed that the slit valve used in the present invention, which is made of a composition containing an ethylene-hexene copolymer, has excellent compatibility when melt-kneaded with the cap base, etc., which is made of a resin whose main component is polypropylene, making material recycling possible.

Furthermore, the presence of tertiary carbon in the polymer chain of ethylene-hexene copolymer reduces its affinity with the oils contained in food (long-chain fatty acids containing linear long-chain alkenyl groups). For this reason, it is believed that the slit valve used in the present invention, which is made of a composition containing ethylene-hexene copolymer, is suppressed from swelling due to the oils in food.

The ethylene-hexene copolymer may have a density of 0.90 g/cm3 ^or less and a tensile modulus of 100 MPa or less. This requirement indicates that a predetermined amount of hexene is copolymerized in the ethylene-hexene copolymer.

In other words, ethylene-hexene copolymers having the density and tensile modulus ranges described above have lower density and tensile modulus than polyethylene, which is a homopolymer of ethylene. This is thought to be because the ethylene chains in the ethylene-hexene copolymer are broken by the hexene units, making it impossible to maintain polyethylene crystals with high density and high tensile modulus.

When the tensile modulus of the ethylene-hexene copolymer is low, at 100 MPa or less, it has excellent discharge properties for the contents and liquid drainage when used as a slit valve.

The density of the ethylene-hexene copolymer constituting the slit valve in the slit valve cap of the present invention is 0.90 g/cm3 or ^less , and may be 0.89 g/cm3 ^or less, or 0.88 g/cm3 ^or less. The density of the ethylene-hexene copolymer is a value measured in accordance with JIS K7112.

The tensile modulus of the ethylene-hexene copolymer constituting the slit valve in the slit valve cap of the present invention is 100 MPa or less, and may be 90 MPa or less, 80 MPa or less, 70 MPa or less, 60 MPa or less, 50 MPa or less, 45 MPa or less, 40 MPa or less, 35 MPa or less, 30 MPa or less, 25 MPa or less, or 20 MPa or less.

The tensile modulus of the ethylene-hexene copolymer may be 5 MPa or more, or 10 MPa or more, from the viewpoint of ensuring the strength and hardness required for a slit valve material. The tensile modulus of the ethylene-hexene copolymer is the tensile modulus (Young's modulus) obtained by conducting a tensile test at a tensile speed of 300 mm/min in accordance with JIS K7161.

(Other materials)
Materials other than the low density polyethylene and ethylene-hexene copolymer constituting the slit valve in the slit valve cap of the present invention are not particularly limited as long as they do not impair the effects of the present invention.

Olefin-based resins and elastomers may be used since they are unlikely to cause compatibility problems during material recycling with polypropylene, which is the material for the cap material and the optional mating ring.

Various additives may also be added depending on the application.

<Configuration of cap with slit valve>
The slit valve cap of the present invention is
A cap substrate;
a slit valve provided at an opening of a mouth portion of a cap base and having a slit that opens in response to an increase in internal pressure of the container,
The cap substrate and the slit valve are each constructed from the materials described above.

In the cap with slit valve of the present invention, the cap base and the slit valve may be assembled and fixed by a fitting ring.

The cap with a slit valve of the present invention can have any shape as long as it satisfies the above requirements and can function as a cap with a slit valve. Below, the configuration of the cap with a slit valve of the present invention will be explained using non-limiting examples.

Figure 1 shows a perspective view for explaining an example of the configuration of a cap with a slit valve of the present invention. Also, Figure 2(a) is a front view of the cap with a slit valve of Figure 1 with the lid closed, and Figure 2(b) is a cross-sectional view along line A-A in Figure 2(a).

The cap (100) with a slit valve in FIG. 1 has a cap base (10) and a slit valve (50) provided at the opening (13) of the mouth (12) of the cap base (10).

The cap base (10) has a cap base hanging part (11) and a mouth part (12) having an opening (13) for projecting the contents while being held on the cap base upper surface part connected to the cap base hanging part (11). In the cap base (10), the mouth part (12) may be formed to project from the center of the cap base upper surface part.

The cap with slit valve (100) is intended to be used by connecting the back side of the cap base (10) (the area not shown, surrounded by the cap base hanging portion (11)) to the container mouth (not shown). The connection between the back side of the cap base (10) and the container mouth may be in any form, for example, a screw-in type, a snap-fit type, a bayonet type, etc.

The cap base (10) of the cap with slit valve (100) in FIG. 1 has a lid body (30) connected via a hinge (20). The lid body (30) can be opened and closed by swinging by the hinge (20).

Figure 1 shows a cap (100) with a slit valve with the lid (30) open. Figure 2(a) shows a front view of the cap (100) with a slit valve with the lid (30) of Figure 1 closed.

The lid (30) may have a lid hanging portion (31) rising from the hinge (20) and a lid flat portion (32) held by the lid hanging portion (31). The lid (30) forms a seal together with the mouth portion (12) when in the closed state. For example, the lid (30) may further have a lid seal forming portion (33) for contacting the mouth portion (12) when in the closed state to form a seal. The lid seal forming portion (33) may have, for example, a ring, fin, pin, insert, sleeve, skirt, etc. to form a seal.

In the cap with slit valve (100) of Figure 1, a slit valve (50) is provided at the opening (13) of the mouth (12) of the cap base (10). This slit valve (50) has a slit that is closed under normal pressure and the contents are retained, but when the container body (not shown) is pressurized to increase the internal pressure of the container, the slit of the slit valve (50) is pushed open by the pressure of the contents, and the contents are discharged. When the pressure of the container body (not shown) is stopped, the slit closes due to its elasticity, and the discharge of the contents is stopped.

In the cap with slit valve (100) of FIG. 1, the slit of the slit valve (50) is cross-shaped, but the shape of the slit can be any shape as long as the contents can be ejected, and it may be radial, linear, etc.

Figure 2(a) is a front view of the cap (100) with slit valve in Figure 1 with the lid (30) of the cap (100) closed. Figure 2(b) is a cross-sectional view taken along line A-A in Figure 2(a), showing an example of the positional relationship between the cap base (10) and the slit valve (50) in the cap (100) with slit valve.

In the cap (100) with slit valve, the slit valve (50) is assembled and fixed by a fitting ring (40) in a recess formed inside the mouth portion (12) of the cap base (10), and is arranged over the entire area of the opening (13). Specifically, the slit valve (50) and the fitting ring (40) are inserted from the back side of the opening (13) of the mouth portion (12) of the cap base (10), and assembled so that the slit valve (50) is sandwiched between the fitting ring (40) and the mouth portion (12) of the cap base (10).

The positional relationship between the cap base (10) and the slit valve (50) in the cap with slit valve (100) is not limited to the embodiment shown in FIG. 2, and may be any other embodiment. In addition, in the cap with slit valve (100), the method of engaging the slit valve (50) with the mouth portion (12) of the cap base (10) is not limited to the embodiment shown in FIG. 2, and may be any known method for attaching a slit valve to a cap with a slit valve.

In the cap with a slit valve of the present invention,
The cap base (10) is made of a resin mainly composed of polypropylene; and the slit valve (50) is made of a composition containing low-density polyethylene and an ethylene-hexene copolymer, which is a copolymer of a monomer mixture containing at least ethylene and hexene; and further,
The cap base and the slit valve may be fixedly assembled.

The shape of the cap with slit valve shown in FIG. 1 is merely one embodiment of the present invention, and the shape of the cap with slit valve of the present invention is not limited to the shape shown in FIG. 1. The cap with slit valve of the present invention can have any shape as long as it can function as a cap with a slit valve.

<Manufacturing method of cap with slit valve>
The cap with a slit valve of the present invention may be manufactured by any method as long as it has the above-mentioned configuration. For example, it may be manufactured by the following method.

Molding a cap base using a resin mainly composed of polypropylene (cap base molding step);
Molding a fitting ring for assembling a valve to a cap base using a resin mainly composed of polypropylene (fitting ring molding process)
Molding a slit valve using a composition containing low density polyethylene and an ethylene-hexene copolymer, which is a copolymer of a monomer mixture containing at least ethylene and hexene (slit valve molding step); and assembling and fixing the cap base and the slit valve with a fitting ring (assembly step).
A manufacturing method (first manufacturing method) of a cap with a slit valve, comprising:

<First manufacturing method>
A first manufacturing method for manufacturing a cap with a slit valve of the present invention includes a cap base molding step, a fitting ring molding step, a slit valve molding step, and an assembling step.

(Cap Base Molding Process and Fitting Ring Molding Process)
In the cap base molding step and the fitting ring molding step, the cap base and the fitting ring are molded using a resin mainly composed of polypropylene. The resin mainly composed of polypropylene may be appropriately selected depending on the desired composition of the cap or the fitting ring. The cap base and the fitting ring may be molded by a known method, for example, by an appropriate molding method such as injection molding, compression molding, vacuum molding, or pressure molding.

(Slit valve molding process)
In the slit valve molding process, a composition containing low-density polyethylene and an ethylene-hexene copolymer, which is a copolymer of a monomer mixture containing at least ethylene and hexene, is used to mold the slit valve. The physical properties of the composition containing low-density polyethylene and an ethylene-hexene copolymer may be appropriately selected depending on the desired characteristics of the slit valve. The slit valve may be molded by a known method, for example, by an appropriate molding method such as injection molding, compression molding, vacuum molding, or pressure molding.

(Assembly process)
In the assembling step, the cap base obtained in the cap base molding step and the slit valve obtained in the slit valve molding step are fixed using the fitting ring obtained in the fitting ring molding step to obtain a cap with a slit valve. For example, the slit valve may be placed on the fitting ring, and the slit valve and the fitting ring may be inserted from the back side of the opening of the mouth part of the cap base, and assembled so that the slit valve is sandwiched between the fitting ring and the mouth part of the cap base.

(When the slit of the slit valve is formed)
The slits in the slit valve may be formed simultaneously with molding of the slit valve, may be formed after molding of the slit valve and before the assembly step, or may be formed after the assembly step.

Materials used in the Examples and Comparative Examples
The materials used in the examples and comparative examples are shown below.
(1) Low density polyethylene: Suntec (registered trademark) M6525 (Asahi Kasei, MFR (190°C): 28g/10min)
(2) Ethylene-hexene copolymer Kernel (registered trademark) KS240T (Japanese polyethylene, MFR (190°C): 2.2g/10min, density (JIS K7112): 0.880g/cm ³ , tensile modulus: 100 or less)
(3) Styrene-based elastomer: AR-850C (Aronkasei, MFR (230°C): 4.0g/10min)
・AR-885C (Aronkasei, MFR (230°C): 10.0g/10min)

Example 1
(Preparation of Slit Valve Composition)
80 parts by mass of low-density polyethylene Santec (registered trademark) M6525 (Asahi Kasei, MFR (190°C): 28 g/10 min) and 20 parts of Kernel (registered trademark) KS240T (Japan Polyethylene, MFR (190°C): 2.2 g/10 min) were mixed to obtain a resin composition for slit valves.

(Fabrication of a slit valve)
The obtained resin composition for slit valves was injection molded to produce a sheet, and a circular sample piece with a diameter of about 13 mm was cut out from the obtained sheet, and a cross slit with a slit length of 12 mm was formed to produce a slit valve. In slit processing, the sample piece was placed on a receiving jig and positioned, and then a slit processing blade (double-sided flat blade, blade length 12 mm, thickness 0.3 mm) was lowered toward the sample piece from above and pressed into the sample piece to form a slit. The membrane thickness of the obtained slit valve was about 300 μm.

Examples 2 to 4 and Comparative Examples 1 to 9
A slit valve was produced in the same manner as in Example 1, except that the materials shown in Table 1 were used.

"evaluation"
The resin compositions for slit valves and the slit valves thus obtained were subjected to the following evaluations. The evaluation results are shown in Table 1.

(1) Valve dischargeability A cap base and a fitting ring were made from random polypropylene (r-PP), the prepared slit valve was placed on the fitting ring, the slit valve and the fitting ring were inserted from the back side of the opening of the mouth of the cap base, and the slit valve was sandwiched between the fitting ring and the mouth of the cap base to prepare a cap with a slit valve. The obtained cap with a slit valve was set in a container that would become the body of the container and store miso seasoning, and the dischargeability of the miso seasoning was evaluated according to the following evaluation criteria.
○: Can be easily discharged △: Can be discharged with a little force ×: Cannot be discharged

(2) Recycle Mixing Property 95 parts by mass of random polypropylene (r-PP) and 5 parts by mass of the material for the slit valve were mixed and crushed, and melt-mixed in a Banbury mixer at 180°C for 10 minutes. About 4 g of the resulting mixture was sandwiched between two sheets of peelable PET (thickness: 25 μm) and heat-pressed for 30 seconds at a temperature of 180°C and a pressure of 20 MPa with a SUS plate to produce a sheet. The appearance of the obtained sheet was visually observed and evaluated according to the following evaluation criteria.
◯: No lumps or yellowing, uniformly kneaded ×: There were lumps or yellowing

(3) Cutting ability (slitting processability)
The appearance of the produced slit valve was visually observed and evaluated according to the following criteria.
〇: Cut without any problems ×: Cut, but there were wrinkles or burrs on the valve

REFERENCE SIGNS LIST 10 Cap base 11 Cap base hanging portion 12 Mouth portion 13 Opening 20 Hinge 30 Lid 31 Lid hanging portion 32 Lid flat portion 33 Lid sealing forming portion 40 Fitting ring 50 Slit valve 100 Cap with slit valve

Claims (6)

A cap substrate;
a slit valve provided at an opening of the mouth of the cap base and having a slit that opens when the internal pressure of the container increases;
A cap with a slit valve, comprising:
The cap base is made of a resin mainly composed of polypropylene, and
The slit valve is a cap with a slit valve, which is composed of a composition including a low density polyethylene and an ethylene-hexene copolymer which is a copolymer of a monomer mixture including at least ethylene and hexene. The cap with slit valve according to claim 1, wherein the ratio of the low-density polyethylene constituting the slit valve is 20 to 80 mass% relative to 100 mass % of the total of the low-density polyethylene and the ethylene-hexene copolymer constituting the slit valve. The cap with a slit valve according to claim 1 or 2, wherein the ethylene-hexene copolymer has a density of 0.90 g/cm3 ^or less and a tensile modulus of elasticity of 100 MPa or less. The cap with a slit valve according to any one of claims 1 to 3, wherein the cap base has a lid body connected via a hinge. The cap with slit valve according to any one of claims 1 to 4, wherein the cap base and the slit valve are assembled and fixed. A method for manufacturing the cap with a slit valve according to claim 5, comprising the steps of:
molding the cap base and the fitting ring using a resin mainly composed of polypropylene;
A method for manufacturing a cap with a slit valve, comprising: molding the slit valve using a composition containing low-density polyethylene and an ethylene-hexene copolymer, which is a copolymer of a monomer mixture containing at least ethylene and hexene; and assembling and fixing the cap base and the slit valve with the fitting ring.

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