GB2552865A

GB2552865A - Foam gasket and preparation method thereof

Info

Publication number: GB2552865A
Application number: GB1704539.4A
Authority: GB
Inventors: Wang Yanping
Original assignee: Jiangsu Jinhou New Material Tech Co Ltd
Current assignee: Jiangsu Jinhou New Material Tech Co Ltd
Priority date: 2016-08-12
Filing date: 2017-03-22
Publication date: 2018-02-14
Anticipated expiration: 2037-03-22
Also published as: CN106317550B; GB2552865B; CN106317550A; WO2018028111A1; GB201704539D0; DE112016000112T5; FR3054974A1; FR3054974B1

Abstract

The foam gasket comprises a substrate layer and a film layer covering the upper and lower surfaces of the substrate layer. The substrate layer is a foam body and a uniform capillary pore body. The average pore diameter of the capillary pores is 1-100 µm. The film layer is uniform and compact. The foam comprises polyethylene (PE) and/or polypropylene (PP), polyethylene octene (POE), styrene butadiene styrene (SBS) and/or styrene ethylene butadiene styrene (SEBS), release agent, and nucleating agent. The film comprises at least two of PE, PP and POE, release agent and anti-block agent. The gasket is formed by extrusion foaming using supercritical carbon dioxide and then extrusion coating. The gasket is used for sealing caps on food and medicine packaging.

Description

(54) Title of the Invention: Foam gasket and preparation method thereof Abstract Title: Foam gasket and production thereof (57) The foam gasket comprises a substrate layer and a film layer covering the upper and lower surfaces of the substrate layer. The substrate layer is a foam body and a uniform capillary pore body. The average pore diameter of the capillary pores is 1-100 pm. The film layer is uniform and compact. The foam comprises polyethylene (PE) and/ or polypropylene (PP), polyethylene octene (POE), styrene butadiene styrene (SBS) and/or styrene ethylene butadiene styrene (SEBS), release agent, and nucleating agent. The film comprises at least two of PE, PP and POE, release agent and anti-block agent. The gasket is formed by extrusion foaming using supercritical carbon dioxide and then extrusion coating. The gasket is used for sealing caps on food and medicine packaging.

Foam gasket and preparation method thereof

Technical field

The present invention belongs to the technical field of high safety fields such as food packaging, medicine packaging and so on, and relates to a foam gasket and a preparation method thereof, and more particularly to a sealing gasket for bottle caps and a preparation method thereof.

Background art

Bottle cap gasket is made of rubber, copper sheet, or paper. It is a material used to fit between two planes to reinforce sealing and has an effect of preventing fluid leakage. With the continuous development of the economy, bottle cap gaskets are widely used in wines, food, cosmetics, pharmaceutical and other industries.

According to the relevant news reports, there is a growing demand currently on bottle cap gaskets in wine packaging and beverage packaging in China, and bottle cap gaskets used in wine packaging cover more than 70% of the total amount of used cap gaskets. With the rapid development of China's wine and beverage industry, bottle cap gasket industry gradually rises. China's bottle cap gasket production in 2014 has a year-on-year increase of 14% compared to 2013, this huge demand not only pulls the price of bottle cap gaskets up all the way, but also makes the number of manufacturers of bottle cap gaskets increase rapidly. At present, China has become the largest consumer and exporter in the world for bottle cap gaskets.

There are as many as hundreds of products in China's bottle cap gasket market, and various specifications and types of bottle cap gaskets exist in the market of food packaging containers. At present, the materials of gaskets used in food packaging are PVC (polyvinyl chloride), PE (polyethylene), Warrior cushion, aluminum foil composite gaskets, paper-plastic-aluminum composite gaskets and others, wherein PVC and PE are the main materials.

CN 104250404A discloses a granule of can bottle cap gasket and its preparation method, wherein the granule of can bottle cap gasket comprises the following materials in parts by mass: 30-50 parts of polypropylene, 30-50 parts of polyethylene, 10-30 parts of a thermoplastic elastomer, and 0.4-5 parts of a processing agent. The granule of can bottle cap gasket is prepared by mixing the above raw materials by a high-speed mixer, extruding by an extruder, cooling, and dicing. The granule of can bottle cap gasket is completely prepared from safe and non-toxic raw materials, free of harmful plasticizers such as phthalates, can meet the safe and non-toxic requirements on the granule of can bottle cap gasket and is excellent in leak tightness.

CN 1465507A discloses a lining material for bottle caps and its application in the hot-filled beverage plastic bottle cap. Said lining material is made of a combination of maleic acid modified EVA (ethylene-vinyl acetate copolymer), SEBS (hydrophenylethylene diene copolymer), hydrogenated paraffin oil, branched low-density polyethylene, polypropylene, polystyrene and low-molecular lubricant. Said lining material comprises EVA having a VA (vinyl acetate) content of 18%, and the weight ratio of the EVA is 5-60%. Ethylene-a-olefin copolymer was added and the weight ratio thereof is 90-35%. This material is not available in conventional cap lining materials. This lining material made by such blending has excellent performances compared with the existing lining material for beverage packaging plastic cap. This gasket material not only is inexpensive, but also has better effects than lining materials of conventional hot-filled beverage plastic bottle caps.

However, the sealability of the existing bottle cap gaskets need to be further improved.

Contents of the Invention

In view of the deficiencies existing in the prior art, the purpose of the present invention is to provide a foam gasket and a preparation method thereof. The foam gasket has good flexibility, softness and elasticity, and is a food-grade plastic sheet, and has excellent sealability when used as a bottle cap gasket. Meanwhile, the preparation method thereof is simple, and easy to be applied in industrial applications.

bar = 0.1 MPa.

In order to achieve the above purpose, the present invention utilizes the following technical solution.

The first purpose of the present invention is to provide a foam gasket comprising a substrate layer and a film layer covering the upper and lower surfaces of the substrate layer. The substrate layer is a foam body and a uniform capillary pore body. The average pore diameter of the capillary pores is 1-100 pm, for example, 2 pm, 5 pm, 8 pm, 10 pm, 12 pm, 15 pm, 18 pm, 20 pm, 30 pm, 40 pm, 50 pm, 60 pm, 80 pm, 90 pm, or 95 pm, etc. The film layer is uniform and compact.

The substrate layer is mainly prepared from the following raw materials in mass percent:

PE (polyethylene), 0-90%, for example 2%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 85%, etc.;

PP (polypropylene), 0-90%, for example 2%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 85%, etc.;

any one of POE (ethylene-octene copolymer), SBS (block copolymer of styrene and butadiene), or SEBS (hydrogenated styrene-butadiene block copolymer), or a combination of at least two of them, 0-20% (not including 0), for example 0.5%, 1%, 2%, 3%, 5%, 6%, 8%, 10%, 12%, 15%, or 18%, etc.;

release agent, 0.2-1.0%, for example 0.3%, 0.5%, 0.6%, 0.7%, 0.8%, or 0.9%, etc.;

nucleating agent, 0.1-2.5%, for example 0.3%, 0.5%, 0.8%, 1.0%, 1.2%, 1.5%, 1.8%, 2.0%, or 2.3%, etc.;

color masterbatch, 0-2.0%, for example 0.1%, 0.5%, 0.8%, 1.0%, 1.2%, 1.3%, 1.5%, 1.7%, or 1.9%, etc.;

wherein at most one substance of PE and PP has a mass percentage of zero; combinations of POE, SBS or SEBS are, for example, a combination of POE and SBS, a combination of POE and SEBS, a combination of POE, SBS and SEBS.

The film layer is mainly prepared from the following raw materials in mass percent:

PE, 0-93%, for example 2%, 3%, 5%, 10%, 20%, 30%, 50%, 60%, 70%, 80%, or 90%, etc.;

PP, 0-95%, for example 1%, 3%, 5%, 8%, 10%, 20%, 30%, 50%, 60%, 80%, or 90%, etc.;

POE, 0-93%, for example 2%, 3%, 5%, 10%, 20%, 30%, 50%, 60%, 70%, 80%, or 90%, etc.;

thickener, 0-30%, for example 1%, 3%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 23%, 25%, or 28%, etc.;

release agent, 0.2-1.1%, for example 0.3%, 0.5%, 0.8%, or 1.0%, etc.;

antiblocking agent, 0.1-3.0%, for example 0.3%, 0.5%, 0.8%, 1.0%, 1.2%, 1.5%, 1.8%, 2.0%, 2.1%, 2.3%, 2.5%, or 2.8%, etc.;

wherein at most one substance of PE, PP and POE has a mass percentage of zero.

The expression of “The substrate layer is a uniform capillary pore body” means that 4 the substrate layer comprises a plurality of capillary pores which are uniformly distributed.

As a preferred embodiment, the substrate layer is prepared from the following raw materials in mass percent:

PE 80%

PP 15% any one of POE, SBS, or SEBS, or a combination of at least two of them 1% release agent 1.0% nucleating agent 2.0% color masterbatch 1%.

Preferably, the release agent is any one selected from the group consisting of oleic acid amide, erucic acid amide, and masterbatch prepared from oleic acid amide and erucic acid amide with PE or PP as a carrier, or a combination of at least two of them. Typical but non-limiting combinations are for example a combination of oleic acid amide and erucic acid amide, a combination of oleic acid amide and masterbatch prepared from oleic acid amide and erucic acid amide with PE or PP as a carrier, and a combination of erucic acid amide and masterbatch prepared from oleic acid amide and erucic acid amide with PE or PP as a carrier.

Preferably, the nucleating agent is selected from masterbatches with sodium bicarbonate and citric acid as the main active ingredients and PE or PP or EVA as a carrier.

As a preferred embodiment, the film layer is mainly prepared from the following raw materials in mass percent:

PE

90%

PP 5%

POE 0.5% thickener 3.5% release agent 0.5% antiblocking agent 0.5%.

Preferably, the thickener is any one selected from the group consisting of EEA (ethylene-ethyl acrylate), polyester, and maleic anhydride grafted resin, or a combination of at least two of them. Typical but non-limiting combinations are for example a combination of EEA and polyester, a combination of EEA and maleic anhydride grafted resin, and a combination of EEA, polyester and maleic anhydride grafted resin.

Preferably, the antiblocking agent is selected from erucic acid amide.

The thickness of the substrate layer is 0.5 to 10.0 mm, for example 0.8 mm, 1.0 mm,

1.5 mm, 2.0 mm, 3.0 mm, 4.0 mm, 5.0 mm, 6.0 mm, 8.0 mm, or 9.0 mm, etc. If the substrate layer is too thick, the application performances such as the sealing 6 performance of the material would be not guaranteed; if it is too thin, the flexibility and coordinating complementary performance of the material would be poor.

Preferably, the density of the substrate layer is 100-800 kg/m³, for example 150 kg/m’ 200 kg/m³, 300 kg/m³, 400 kg/m³, 500 kg/m³, 600 kg/m³, or 700 kg/m³, etc.

The substrate layer is excellent in crosslinking sealing property since it is formed by supercritical physical foaming.

Preferably, the thickness of the fdm layer is 0.02 to 0.15 mm, for example 0.05 mm, 0.08 mm, 0.10 mm, 0.12 mm, or 0.14 mm, etc. If the film layer is too thick, the flexibility and coordinating complementary performance of the material would be poor; if the film layer is too thin, the application performances such as the sealing performance of the material would be not guaranteed. The expression “the thickness of the film layer is 0.02 to 0.15 mm” means that the thickness of the film layer on the upper surface of the substrate layer and the thickness of the film layer on the lower surface of the substrate layer are independently 0.02 to 0.15 mm.

The film layer makes the foam gasket meet sealing functional requirement, while allowing it have good flexibility matching performance.

The second purpose of the present invention is to provide a method for preparing the foam gasket described above, and the method comprises the following steps:

(1) The raw materials of the substrate layer with formula amounts are fed into the hopper of a single screw extruder, while supercritical carbon dioxide is charged in the middle of the single screw extruder. After extruding and foaming, a substrate layer is obtained. The supercritical carbon dioxide is a supercritical carbon dioxide under a pressure of 50 to 220 bar, for example a supercritical carbon dioxide under a pressure of 60 bar, 80 bar, 90 bar, 100 bar, 120 bar, 150 bar, 180 bar, or 200 bar;

(2) The raw materials of the film layer with formula amounts are fed into the hopper of the single screw extruder, coated onto the surface of the substrate layer to form a film, and thereby a foam gasket is obtained.

The single screw extruder in step (1) is a single screw extruder having heating, cooling and pressure resistance performances. Atypical but non-limiting single screw extruder is, for example, a foaming machine manufactured by Berstorff GmbH: 150-ISO-PAC.

In step (1), the host temperature of the single screw extruder during the extrusion process is less than or equal to 65°C, for example 63 °C, 60°C, 58°C, 55°C, 50°C, 45°C, or 30°C, etc. If the host temperature is too high, damage to the units will be caused.

Preferably, the extrusion temperature in step (1) is 90-210°C, for example 100°C, 110°C, 130°C, 150°C, 180°C, 190 °C, or 200°C, etc. If the extrusion temperature is too high, the film forming performance would be not good, the film would have an uneven thickness, and the foaming would be uneven. If the extrusion temperature is too low, the film would be unevenly foamed or foaming would not perform.

Preferably, the rotational speed of the screw during the extrusion process in step (1) is 1-100 rpm, for example 2 rpm, 3 rpm, 5 rpm, 10 rpm, 20 rpm, 30 rpm, 40 rpm, 50 rpm, 60 rpm, 70 rpm, 80 rpm, or 90 rpm, etc.

Preferably, the single screw extruder in step (1) has a bearing pressure range of 0 to 250 bar, for example 2 bar, 5 bar, 10 bar, 20 bar, 50 bar, 100 bar, 120 bar, 150 bar, 180 bar, 200 bar, 220 bar, or 240 bar, etc.

The flow rate of the supercritical carbon dioxide in step (1) is 0.10-2.50 kg/h, for example 0.3 kg/h, 0.5 kg/h, 0.8 kg/h, 1.0 kg/h, 1.2 kg/h, 1.5 kg/h, 1.8 kg/h, 2.0 kg/h, or 2.3 kg/h, etc. If the flow rate is high, the film would be foamed unevenly and excessively, and the material would fail in elasticity. If the flow rate is low, the foaming would be too low and the flexibility would not be enough.

Preferably, the thickness of the substrate layer in step (1) is 0.5-10.0 mm, for example 0.8 mm, 1.0 mm, 1.5 mm, 2.0 mm, 3.0 mm, 4.0 mm, 5.0 mm, 6.0 mm, 8.0 mm, or 9.0 mm, etc.

□

Preferably, the density of the substrate layer in step (1) is 100-800 kg/m , for example 150 kg/m³, 200 kg/m³, 300 kg/m³, 400 kg/m³, 500 kg/m³, 600 kg/m³, or 700 kg/m³.

The extrusion temperature in step (2) is 80-250°C, for example 85°C, 90°C, 95°C, 100°C, 120°C, 130°C, 150°C, 180°C, 200°C, 210°C, 220°C, or 240°C, etc.

Preferably, the rotational speed of the screw during the extrusion process in step (2) is 1-100 rpm, for example 2 rpm, 3 rpm, 5 rpm, 10 rpm, 20 rpm, 30 rpm, 40 rpm, 50 rpm, 60 rpm, 70 rpm, 80 rpm, or 90 rpm, etc.

The thickness of the film covering the substrate layer in step (2) is 0.02-0.15 mm, for example 0.05 mm, 0.08 mm, 0.10 mm, 0.12 mm, or 0.14 mm, etc.

The coated-film in step (2) can be prepared as a functional film according to the downstream application requirements.

As a preferred embodiment, the preparation method comprises the following steps:

(1) The raw materials of the substrate layer with formula amounts are fed into the hopper of a single screw extruder, while supercritical carbon dioxide under a pressure of 50-220 bar is charged in the middle of the single screw extruder at a flow rate of 0.10-2.50 kg/h. After extruding, a substrate layer having a density of 100-800 kg/m³ and a thickness of 0.5-10.0 mm is obtained. Wherein the host temperature of the single screw extruder during the extrusion process is less than or equal to 65°C, the extrusion temperature is 90-210°C, the rotational speed of the screw during the extrusion process is 1-100 rpm, and the bearing pressure range of the single screw extruder is 0-250 bar;

(2) The raw materials of the film layer with formula amounts are fed into the hopper of the single screw extruder, coated onto the surface of the substrate layer to form a film, and thereby a foam gasket having a covering film thickness of 0.02-0.15 mm is obtained. Wherein the extrusion temperature is 80-250°C, and the rotational speed of the screw during the extrusion process is 1-100 rpm.

Compared with the prior art, the present invention has the following beneficial effects:

The foam gasket provided by the present invention is composed of a substrate layer and a film layer. The substrate layer is made by foaming, and the cross-linking sealing property, flexibility, softness and elasticity thereof are better. The film covering the substrate layer makes the foam gasket possess good flexibility matching performance and meet sealing functional requirement. The Shore A hardness of the foam gasket is 35-50. The foam gasket has excellent sealing performance and good opening performance when used as a bottle cap gasket, and also has the effects of bonding and improving the flatness. In addition, the foam gasket is a food-grade plastic sheet.

The preparation method of the foam gasket provided by the present invention is simple and convenient for industrial application.

Embodiments

The technical solution of the present invention is further explained by combining with the following specific embodiments.

In the method of the following examples, the single screw extruder in step (1) is a single screw extruder having heating, cooling and pressure resistance performances—a foaming machine manufactured by Berstorff GmbH: 150-ISO-PAC.

In the following examples, the thickness of the film layer described as a certain number means that the thickness of the film layer on the upper surface of the substrate io layer and the thickness of the film layer on the lower surface of the substrate layer are independently a certain number.

Example 1

A foam gasket comprises a substrate layer and a film layer covering the upper and lower surfaces of the substrate layer. The substrate layer is a foam body and a uniform capillary pore body. The average pore diameter of the capillary pores is 1-30 pm. The film layer is a coated-film layer, and is uniform and compact. The substrate layer has a thickness of 0.5 mm. The film layer has a thickness of 0.02 mm.

PE 90%

POE

9.7% release agent nucleating agent

0.2%

0.1%;

the release agent is selected from oleic acid amide;

the nucleating agent is selected from a masterbatch with sodium bicarbonate and citric acid as the main active ingredients and PE or PP or EVA as a carrier.

PE

POE

93%

2.9% release agent

1.1% antiblocking agent

3.0%;

the thickener is selected from EEA (ethylene-ethyl acrylate);

the release agent is selected from oleic acid amide;

the antiblocking agent is selected from erucic acid amide.

The method for preparing the foam gasket comprises the following steps:

(1) The raw materials of the substrate layer with formula amounts were fed into the hopper of a single screw extruder, while supercritical carbon dioxide under a pressure of 50 bar was charged in the middle of the single screw extruder at a flow rate of 2.50 kg/h. After extruding and foaming, a substrate layer was obtained. Wherein the host temperature of the single screw extruder during the extrusion process was 65°C, the extrusion temperature was 210°C, the rotational speed of the screw during the extrusion process was 1 rpm, and the bearing pressure range of the single-screw extruder was 250 bar;

(2) The raw materials of the film layer with formula amounts were fed into the hopper of the single screw extruder, coated onto the surface of the substrate layer to form a film, and thereby a foam gasket having a covering film thickness of 0.02 mm was obtained. Wherein the extrusion temperature was 80°C, and the rotational speed of the screw during the extrusion process was 100 rpm.

Example 2

A foam gasket comprises a substrate layer and a film layer covering the upper and lower surfaces of the substrate layer. The substrate layer is a foam body and a uniform capillary pore body. The average pore diameter of the capillary pores is 50-100 pm. The film layer is a coated-film layer, and is uniform and compact. The substrate layer has a thickness of 10.0 mm. The film layer has a thickness of 0.15 mm.

PP 90%

SBS 4.5% release agent 1.0% nucleating agent 2.5% color masterbatch 2.0%;

the release agent is selected from oleic acid amide and erucic acid amide.

Preferably, the nucleating agent is selected from a masterbatch with sodium bicarbonate and citric acid as the main active ingredients and PE or PP or EVA as a carrier.

PP 95%

POE 3.7% thickener 1% release agent 0.2% antiblocking agent 0.1%;

the thickener is selected from EEA and polyester;

the release agent is selected from a masterbatch prepared from oleic acid amide and erucic acid amide with PE or PP as a carrier.

the antiblocking agent is selected from erucic acid amide.

The method for preparing the foam gasket comprises the following steps:

(1) The raw materials of the substrate layer with formula amounts were fed into the hopper of a single screw extruder, while supercritical carbon dioxide under a pressure of 220 bar was charged in the middle of the single screw extruder at a flow rate of 0.10 kg/h. After extruding and foaming, a substrate layer was obtained. Wherein the host temperature of the single screw extruder during the extrusion process was 50°C, the extrusion temperature was 90°C, the rotational speed of the screw during the extrusion process was 100 rpm, and the bearing pressure range of the single-screw extruder was 100 bar;

(2) The raw materials of the fdm layer with formula amounts were fed into the hopper of the single screw extruder, coated onto the surface of the substrate layer to form a fdm, and thereby a foam gasket having a covering fdm thickness of 0.15 mm was obtained. Wherein the extrusion temperature was 250°C, and the rotational speed of the screw during the extrusion process was 1 rpm.

Example 3

A foam gasket comprises a substrate layer and a fdm layer covering the upper and lower surfaces of the substrate layer. The substrate layer is a foam body and a uniform capillary pore body. The average pore diameter of the capillary pores is 30-80 pm. The fdm layer is a coated-fdm layer, and is uniform and compact. The substrate layer has a thickness of 5.0 mm. The film layer has a thickness of 0.10 mm.

PE 50%

PP 26.5%

SEBS 20% release agent 0.5% nucleating agent 2.0% color masterbatch 1.0%;

the release agent is selected from erucic acid amide.

PE 1%

PP 1%

POE 93% thickener 2% release agent E0% antiblocking agent 2.0%.

The thickener is selected from maleic anhydride grafted resin.

The antiblocking agent is selected from erucic acid amide.

The method for preparing the foam gasket comprises the following steps:

(1) The raw materials of the substrate layer with formula amounts were fed into the hopper of a single screw extruder, while supercritical carbon dioxide under a pressure of 100 bar was charged in the middle of the single screw extruder at a flow rate of 1.00 kg/h. After extruding and foaming, a substrate layer was obtained. Wherein the host temperature of the single screw extruder during the extrusion process was 60°C, the extrusion temperature was 120°C, the rotational speed of the screw during the extrusion process was 20 rpm, and the bearing pressure range of the single screw extruder was 120 bar;

(2) The raw materials of the film layer with formula amounts were fed into the hopper of the single screw extruder, coated onto the surface of the substrate layer to form a film, and thereby a foam gasket having a covering film thickness of 0.10 mm was obtained. Wherein the extrusion temperature was 100°C, and the rotational speed of the screw during the extrusion process was 20 rpm.

Example 4

A foam gasket comprises a substrate layer and a film layer covering the upper and lower surfaces of the substrate layer. The substrate layer is a foam body and a uniform capillary pore body. The average pore diameter of the capillary pores is 1-30 pm. The film layer is a coated-film layer, and is uniform and compact. The substrate layer has a thickness of 3.0 mm. The film layer has a thickness of 0.05 mm.

PE 60%

PP 30%

POE and SBS with a mass ratio of 1:1 7% release agent 0.5% nucleating agent 1.5% color masterbatch 1.0%.

PE 18.5%

PP 30%

POE 20% thickener 30% release agent 0.5% antiblocking agent 1.0%.

Preferably, the thickener is selected from a combination of EEA, polyester and maleic anhydride grafted resin with a mass ratio of 1:1:1.

The release agent is selected from oleic acid amide.

The antiblocking agent is selected from erucic acid amide.

The method for preparing the foam gasket comprises the following steps:

(1) The raw materials of the substrate layer with formula amounts were fed into the hopper of a single screw extruder, while supercritical carbon dioxide under a pressure of 150 bar was charged in the middle of the single screw extruder at a flow rate of 2.0 kg/h. After extruding and foaming, a substrate layer was obtained. Wherein the host temperature of the single screw extruder during the extrusion process was 55°C, the extrusion temperature was 170°C, the rotational speed of the screw during the extrusion process was 80 rpm, and the bearing pressure range of the single-screw extruder was 150 bar;

(2) The raw materials of the film layer with formula amounts were fed into the hopper of the single screw extruder, coated onto the surface of the substrate layer to form a film, and thereby a foam gasket having a covering film thickness of 0.05 mm was obtained. Wherein the extrusion temperature was 180°C, and the rotational speed of the screw during the extrusion process was 90 rpm.

Example 5

A foam gasket comprises a substrate layer and a film layer covering the upper and lower surfaces of the substrate layer. The substrate layer is a foam body and a uniform capillary pore body. The average pore diameter of the capillary pores is 1-100 pm. The film layer is a coated-film layer, and is uniform and compact. The substrate layer has a thickness of 3.0 mm. The film layer has a thickness of 0.05 mm.

PE 80%

PP 15%

POE 1% release agent 1.5% nucleating agent 1.5% color masterbatch 1%.

The release agent is selected from oleic acid amide.

PE 90%

PP 5%

POE 0.5% thickener 3.5% release agent 0.5% antiblocking agent 0.5%.

The thickener is selected from maleic anhydride grafted resin.

The antiblocking agent is selected from erucic acid amide.

The method for preparing the foam gasket comprises the following steps:

Comparative Example 1

The product of comparative example 1 is the substrate layer prepared in Example 3.

Comparative Example 2

The product of comparative example 2 is a commercially available PE gasket (Manufacturer: Shanghai Mingyuan Plastic Products Co., Ltd).

Comparative Example 3

A foam gasket and its preparation method, which are the same as those in Example 5, except that the flow rate of supercritical carbon dioxide is 0.08 kg/h.

Comparative Example 4

A foam gasket and its preparation method, which are the same as those in Example 5, except that the flow rate of supercritical carbon dioxide is 2.60 kg/h.

The properties of the products obtained in Examples 1 to 5 and Comparative Examples 1 to 4 were tested. The test methods for density, flexibility, Shore hardness and sealability are respectively GB1033, perceptual test, GB2411, and self-made oil penetration method (a glass bottle filled with edible oil was sealed by a bottle cap made of the foam gaskets, and side-placed on a platform paved with a white paper. After 10 days, observation was carried out to confirm whether or not the oil was penetrated onto the white paper. If yes, it is not qualified; if not, it is qualified) The test results are shown in table 1.

Table 1

	Density	Flexibility	Shore A hardness	Sealability when used as a bottle cap
Example 1	300 g/L	excellent	50	qualified
Example 2	288 g/L	good	51	qualified
Example 3	425 g/L	excellent	45	qualified
Example 4	403 g/L	good	48	qualified
Example 5	389 g/L	excellent	35	qualified
Comparati ve Example 1	305 g/L	common	57	qualified
Comparati	297 g/L	common	60	qualified

ve Example 2
Comparati ve Example 3	412 g/L	common	65	qualified
Comparati ve Example 4	263 g/L	common	62	qualified

It can be seen that the foam gasket provided by the present invention has excellent performances and is excellent in sealing performance as a bottle cap gasket. In addition, the present invention provides a foam gasket which meets food-grade requirements and can be widely used in high safety areas such as food packaging and pharmaceutical packaging and so on.

The applicant states that the present invention illustrates detailed methods of the present invention by the above examples, but the present invention is not limited to the above examples, that is to say, it does not mean that the present invention must be conducted relying on the above examples. Those skilled in the art should understand that any modification to the present invention, any equivalent replacement of each raw material of the products of the present invention and the addition of auxiliary ingredients, the selection of specific embodiment and the like all fall into the protection scope and the disclosure scope of the present invention.

Claims

1. A foam gasket, characterized in that the foam gasket comprises a substrate layer and a film layer covering the upper and lower surfaces of the substrate layer; the substrate layer is a foam body and a uniform capillary pore body; the average pore diameter of the capillary pores is 1-100 pm;

PE 0-90% PP 0-90% any one of POE, SBS or SEBS, or a combination of at least two of them 0-20% (not including 0)

release agent 0.2-1.0% nucleating agent 0.1-2.5% color masterbatch 0-2.0%;

wherein at most one substance of PE and PP has a mass percentage of zero;

the film layer is mainly prepared from the following raw materials in mass percent

PE 0-93%

PP 0-95% POE 0-93% thickener 0-30%

release agent

0.2-1.1% antiblocking agent 0.1 -3.0%;

wherein at most one substance of PE, PP and POE has a mass percentage of zero.

2. The foam gasket of claim 1, characterized in that the substrate layer is mainly prepared from the following raw materials in mass percent:

PE 80%

PP 15% any one of POE, SBS or SEBS, or a combination of at least two of them 1% release agent 1.0% nucleating agent 2.0% color masterbatch 1%.

3. The foam gasket of claim 1 or 2, characterized in that the release agent is any one selected from the group consisting of oleic acid amide, erucic acid amide, and masterbatch prepared from oleic acid amide and erucic acid amide with PE or PP as a carrier, or a combination of at least two of them.

4. The foam gasket of any one of claims 1-3, characterized in that the nucleating agent is selected from masterbatches with sodium bicarbonate and citric acid as the main active ingredients and PE or PP or EVA as a carrier.

5. The foam gasket of any one of claims 1-4, characterized in that the film layer is mainly prepared from the following raw materials in mass percent:

PE 90%

PP

5%

POE

0.5% thickener release agent antiblocking agent

3.5%

0.5%

0.5%;

preferably, the thickener is any one selected from the group consisting of EEA, polyester, and maleic anhydride grafted resin, or a combination of at least two of them;

preferably, the release agent is any one selected from the group consisting of oleic acid amide, erucic acid amide, and masterbatch prepared from oleic acid amide and erucic acid amide with PE or PP as a carrier, or a combination of at least two of them;

preferably, the antiblocking agent is selected from erucic acid amide.

6. The foam gasket of any one of claims 1-5, characterized in that the thickness of the substrate layer is 0.5 to 10.0 mm;

□ preferably, the density of the substrate layer is 100-800 kg/m ;

preferably, the thickness of the film layer is 0.02 to 0.15 mm.

7. A method for preparing the foam gasket of any one of claims 1-6, characterized in that the method comprises the following steps:

(1) The raw materials of the substrate layer with formula amounts are fed into the hopper of a single screw extruder, while supercritical carbon dioxide is charged in the middle of the single screw extruder; a substrate layer is obtained by extruding and foaming; the supercritical carbon dioxide is a supercritical carbon dioxide under a 25 pressure of 50 to 220 bar;

(2) The raw materials of the film layer with formula amounts are fed into the hopper of the single screw extruder, coated onto the surface of the substrate layer to form a film, and thereby the foam gasket is obtained.

8. The method of claim 7, characterized in that the host temperature of the single screw extruder during the extrusion process is less than or equal to 65°C;

preferably, the extrusion temperature in step (1) is 90-210°C;

preferably, the rotational speed of the screw during the extrusion process in step (1) is 1-100 rpm;

preferably, the bearing pressure range of the single screw extruder in step (1) is 0 to 250 bar.

9. The method of claim 7 or 8, characterized in that the flow rate of the supercritical carbon dioxide in step (1) is 0.10-2.50 kg/h;

preferably, the thickness of the substrate layer in step (1) is 0.5-10.0 mm;

□ preferably, the density of the substrate layer in step (1) is 100-800 kg/m .

10. The method of any one of claims 7-9, characterized in that the extrusion temperature in step (2) is 80-250°C;

preferably, the rotational speed of the screw during the extrusion process in step (2) is 1-100 rpm.

11. The method of any one of claims 7-10, characterized in that the thickness of the film covering the substrate layer in step (2) is 0.02-0.15 mm.

12. The method of any one of claims 7-11, characterized in that the method comprises the following steps:

(1) The raw materials of the substrate layer with formula amounts are fed into the hopper of a single screw extruder, while supercritical carbon dioxide under a pressure of 50-220 bar is charged in the middle of the single screw extruder at a flow rate of 0.10-2.50 kg/h; After extruding and foaming, a substrate layer having a density of 100-800 kg/m3 and a thickness of 0.5-10.0 mm is obtained; wherein the host temperature of the single screw extruder during the extrusion process is less than or equal to 65°C, the extrusion temperature is 90-210°C, the rotational speed of the screw during the extrusion process is 1-100 rpm, and the bearing pressure range of the single-screw extruder is 0-250 bar;

(2) The raw materials of the film layer with formula amounts are fed into the hopper of the single screw extruder, coated onto the surface of the substrate layer to form a film, and thereby a foam gasket having a covering film thickness of 0.02-0.15 mm is obtained; wherein the extrusion temperature is 80-250°C, and the rotational speed of the screw during the extrusion process is 1-100 rpm.

Intellectual

Property

Office

Application No: Claims searched:

GB1704539.4

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