KR102738535B1 - Foam sheet having improved surface roughness - Google Patents

Abstract

The present invention relates to a foam sheet with improved surface roughness, and provides a foam sheet including a skin layer formed from the surface to a depth of 150 ㎛, wherein the cell density of the foam sheet is 160,000/cm3 or more, and the surface roughness (Ra) of the skin layer is 2 ㎛ or less.

Description

Foam sheet having improved surface roughness

The present invention relates to a foam sheet, and more particularly to a foam sheet having improved surface roughness.

The recent automotive industry trend requires lightweight, VOC reduction, insulation, cushioning, and high strength for the environment. In particular, foam materials are being actively developed for lightweight energy saving. Cross-linked PP Foam and PU Foam have been widely used since the past, but these products are not recyclable and have the disadvantage of having to use reinforcing materials due to their weak rigidity.

The most commonly used material for trunk interiors of automobiles is PP non-foam sheet, which is then combined with PET non-woven fabric to create a composite material, which is then cold-formed to create a shape. This composite material uses different materials, so the scrap left after molding must be disposed of, and the shape stability after molding is poor, resulting in a high defect rate.

The materials that are widely used as headliners are mainly PUGF (a material that is a composite of PU Foam and Glass Fiber) and PPGF (a material that is a composite of PP Foam and Glass Fiber). However, these composites also use different materials, so they are not recycled, and the thickness increases to maintain rigidity, and a large amount of adhesive is used for wood polymerization, so there are disadvantages in that VOCs increase.

The application of PET melt extrusion foam sheet of the physical foam type that can be recycled by using PET material, which has low carbon emissions during the manufacturing process and is the same material as PET non-woven fabric, is being promoted. However, it has the disadvantage of being difficult to process due to lack of formability in parts with complex shapes and deep areas. Therefore, it is necessary to develop automobile interior materials with excellent processability of PET foam sheet.

The purpose of the present invention is to provide a foam sheet having improved surface roughness and an automobile interior material formed therefrom.

In order to achieve the above-described object, the present invention provides a foam sheet including a skin layer formed from a surface to a depth of 150 ㎛, wherein the cell density of the foam sheet is 160,000/cm3 or more, and the surface roughness (Ra) of the skin layer is 2 ㎛ or less.

In the present invention, the foam sheet can be formed from a composition containing 3 to 5 parts by weight of a thickener and 1.5 to 5 parts by weight of a nucleating agent per 100 parts by weight of resin.

In the present invention, the intrinsic viscosity (IV) of the composition may be 0.9 to 1 ㎗/g.

In the present invention, the density of the skin layer may be 500 kg/㎥ or more.

In the present invention, the cell size of the core layer, which is a region excluding the skin layer among the foam sheets, may be 200 to 400 ㎛.

In addition, the present invention provides an automobile interior material made of the foam sheet described above.

The automobile interior material according to the present invention can be made of a polyethylene terephthalate (PET) single composite material including a PET nonwoven fabric laminated on one or both sides of a foam sheet.

The automobile interior material according to the present invention can have a three-dimensional shape having a depth of 10 cm or more.

According to the present invention, the surface roughness and formability of the foamed sheet can be improved by controlling the viscosity, nucleating agent, thickener, etc.

Hereinafter, the present invention will be described in detail.

The present invention relates to a foam sheet having improved surface roughness.

The foam sheet according to the present invention is a foam sheet including a skin layer formed from the surface to a depth of 150 ㎛, and is characterized in that the cell density of the foam sheet is 160,000/cm3 or more and the surface roughness (Ra) of the skin layer is 2 ㎛ or less.

The cell density of the foam sheet may be 160,000 ea/cm3 or more, for example, 160,000 to 500,000 ea/cm3, 160,000 to 450,000 ea/cm3 or 160,000 to 400,000 ea/cm3. The cell may mean a microstructure expanded by foaming within the polymer.

The surface roughness of the skin layer may be 2 ㎛ or less, for example, 1 to 2 ㎛, 1.2 to 1.95 ㎛, or 1.3 to 1.9 ㎛. The surface roughness may be a centerline surface roughness (Ra).

The foam sheet according to the present invention may have a multilayer structure including a skin layer and a core layer. The skin layer may be formed on one or both of the upper surface and the lower surface of the foam sheet. The skin layer may be formed to a depth of 150 ㎛, 100 ㎛, 50 ㎛, 10 ㎛, or 5 ㎛ from the surface of the foam sheet. That is, the thickness of the skin layer may be 5 to 150 ㎛, 10 to 100 ㎛, or 20 to 80 ㎛.

The core layer refers to the remaining area of the foam sheet excluding the skin layer, and can occupy most of the volume and thickness of the foam sheet. That is, the skin layer can be formed on one or both sides of the core layer, and can be placed on the surface when manufactured as an automobile interior material.

The skin layer is close to a non-foamed layer having few foam cells, and the core layer can be a foamed layer. The cell density of the skin layer can be, for example, 150,000/cm3 or less, 100,000/cm3 or less, 50,000/cm3 or less, or 10,000/cm3 or less. The cell density of the core layer can be the same as or similar to the cell density of the foamed sheet, and can be, for example, 160,000 to 500,000/cm3, 160,000 to 450,000/cm3, or 160,000 to 400,000/cm3.

The foam sheet can be formed from a foaming composition including a resin, a thickener, a nucleating agent, a foaming agent, and the like.

As the resin, for example, a polyester resin can be used. As the polyester resin, for example, at least one selected from among polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polylactic acid (PLA), polyglycolic acid (PGA), polyethylene adipate (PEA), polyhydroxyalkanoate (PHA), polytrimethylene terephthalate (PTT), and polyethylene naphthalene (PEN) can be used, and polyethylene terephthalate (PET) can be preferably used. By using PET resin, it can be environmentally friendly and easy to reuse.

A thickener is included to control the melt viscosity of the foaming composition, and examples thereof include pyromellitic dianhydride (PMDA), epoxy, etc.

The content of the thickener may be 3 to 5 parts by weight (phr), 3 to 4 parts by weight, or 3 to 3.5 parts by weight based on 100 parts by weight of the resin. If the content of the thickener is too low, the density of the polymer, skin layer, or foam sheet may increase. Even if the content of the thickener is too high, especially 5 parts by weight or more, there may be no further change in the melt viscosity, etc.

Nucleating agents are used to control cell density, and examples of inorganic compounds that can be used include talc, mica, silica, diatomaceous earth, alumina, titanium oxide, zinc oxide, magnesium oxide, magnesium hydroxide, aluminum hydroxide, calcium hydroxide, potassium carbonate, calcium carbonate, magnesium carbonate, potassium sulfate, barium sulfate, sodium bicarbonate, and glass beads.

The content of the nucleating agent may be 1.5 to 5 parts by weight, 1.5 to 4.5 parts by weight, or 2 to 4 parts by weight based on 100 parts by weight of the resin. If the content of the nucleating agent is too small, the cell density may be low and the surface roughness may be poor. If the content of the nucleating agent is too large, corrugation may occur on the surface of the sheet.

A blowing agent is added to foam the composition and control the density of the foam sheet, and examples thereof include gases such as N ₂ , CO ₂ , and freon; physical blowing agents such as butane, pentane, neopentane, hexane, isohexane, heptane, isoheptane, and methyl chloride; and chemical blowing agents such as azodicarbonamide compounds, P,P'-oxybis(benzenesulfonylhydrazide) compounds, and N,N'-dinitrosopentamethylenetetramine compounds.

The content of the foaming agent may be 0.1 to 5 parts by weight, 0.5 to 4.5 parts by weight, 1 to 4 parts by weight, 1.5 to 3 parts by weight, or 2 to 2.5 parts by weight based on 100 parts by weight of the resin.

In addition, the foam composition may additionally contain a surfactant, an ultraviolet blocker, a hydrophilizing agent, a flame retardant, a heat stabilizer, a waterproofing agent, a cell size expander, an infrared attenuator, a plasticizer, a fire retardant, a pigment, an elastic polymer, an extrusion aid, an antioxidant, a filler, an anti-foaming agent, a UV absorber, etc., for the purpose of imparting a hydrophilizing function, a waterproofing function, a flame retardant function, a UV blocking function, etc.

The intrinsic viscosity (IV) of the foaming composition can be from 0.9 to 1 ㎗/g, from 0.9 to 0.95 ㎗/g, or from 0.93 to 0.95 ㎗/g.

The density of the foam sheet can be 190 kg/㎥ or less, for example, 50 to 190 kg/㎥, 100 to 180 kg/㎥, or 150 to 170 kg/㎥. The density of the skin layer can be 500 kg/㎥ or more, for example, 500 to 1500 kg/㎥, 500 to 1000 kg/㎥, or 500 to 700 kg/㎥. The density of the core layer can be the same as or similar to the foam sheet, for example, 50 to 190 kg/㎥, 100 to 180 kg/㎥, or 150 to 170 kg/㎥.

The cell size of the core layer may be 200 to 400 μm, or 250 to 350 μm. The cell size of the skin layer may be 100 μm or less, 50 μm or less, 10 μm or less, 5 μm or less, or 1 μm or less.

Foam sheets can be formed through bead foaming or extrusion foaming. Bead foaming is a method of heating beads to foam them first, maturing them for an appropriate amount of time, filling them into molds such as plate shapes and cylinders, heating them again, and fusing and forming them through secondary foaming to create a product. Extrusion foaming simplifies the process steps by continuously extruding and foaming a resin melt, enables mass production, and prevents cracks and granular destruction between beads during bead foaming, thereby realizing better compressive strength.

The skin layer and the core layer constituting the foam sheet can be formed continuously during the process of manufacturing the foam sheet. That is, the skin layer and the core layer can be formed continuously without a separate additional step during the process of manufacturing the foam sheet. For example, the skin layer and the core layer can be formed simultaneously through coextrusion, or the skin layer can be formed on one or both sides of the foam sheet by rapidly cooling the surface of the foam sheet manufactured through extrusion and foaming. That is, the skin layer can be formed by rapidly cooling the foam sheet, or can be manufactured by coextruding a plastic resin to form a coating layer. The rapid cooling can be performed in a temperature range of -30°C to 0°C, -25°C to -10°C, or -20°C to -15°C.

In addition, the present invention provides an automobile interior material made of the foam sheet described above.

The automobile interior material according to the present invention can be made of a polyethylene terephthalate (PET) single composite material including a PET nonwoven fabric laminated on one or both sides of a foam sheet.

The automobile interior material according to the present invention may have a three-dimensional shape having a depth of 10 cm or more, for example, 10 to 50 cm, 20 to 40 cm, or 25 to 35 cm.

The automobile interior material according to the present invention may be a trunk interior material, a headliner, or the like, which is a part with a complex shape and a deep portion.

In this way, in the present invention, by controlling the intrinsic viscosity of the foam composition, the content of the nucleating agent and the thickener, etc., the surface roughness of the foam sheet can be improved, and the formability can be excellent.

Hereinafter, the present invention will be described in more detail by way of examples.

[Examples and Comparative Examples]

Based on 100 parts by weight of PET resin, the contents of the thickener (PMDA), nucleating agent (calcium carbonate), and blowing agent (butane) were varied as shown in Table 1, and the foamed composition was extruded and foamed. Then, the temperature of the cylindrical mandrel, which is a cooling device, was maintained at -20°C to rapidly cool the surface of the foamed sheet, thereby manufacturing a foamed sheet including a skin layer. Then, a luggage side having a deep shape of 30 cm was manufactured using a male and female mold.

[Example]

For the examples and comparative examples, the intrinsic viscosity of the foam composition, the density of the foam sheet, the cell density of the foam sheet, the surface roughness of the skin layer, and the formability were measured, and the results are shown in Table 1.

(1) Intrinsic viscosity (IV)

The intrinsic viscosity was measured at 35°C using an Ubbelohde viscometer by dissolving the foaming composition in a concentration of 0.5 wt% in a mixed solution of phenol and tetrachloroethane (mixing ratio = 1:1 by weight).

(2) Density

Density was measured using EW-300SG from Alfa Mirage under KS M ISO 845 conditions.

(3) Cell density

Cell density was determined by counting the number of cells within a certain unit area using a scanning electron microscope (SEM) image and converting it to ㎤.

(4) Surface roughness

The centerline surface roughness value was measured according to KS B 0161.

(5) Formability

Formability was evaluated by measuring the number of folded or broken areas as 0 good, 1 to 3 average, and 5 or more poor.

Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Thickener (by weight) 3 3 3 1 3 Nuclear agent (by weight) 2 3 4 2 1 Foaming agent (by weight) 2 2 2 2 2 Intrinsic viscosity (㎗/g) 0.93 0.95 0.95 0.88 0.93 Density (kg/㎥) 170 170 170 200 170 Cell density (cells/cm3) 160,000 240 thousand 400 thousand 140 thousand 130 thousand Surface roughness (㎛) 1.9 1.5 1.3 2.1 2.3 Formability Good Good Good error error

As can be seen in Table 1, in the case of the examples, by using an appropriate amount of thickener and nucleating agent, an appropriate range of intrinsic viscosity (0.93 to 0.95 ㎗/g), density (170 kg/㎥), and cell density (160,000 to 400,000/㎤) could be obtained, and the surface roughness (Ra) was improved to 2 ㎛ or less, and the formability was excellent.

In the case of Comparative Example 1, the thickener content was too low at 1 part by weight, so the intrinsic viscosity was low at 0.88 ㎗/g, the density was high at 200 kg/㎥, the cell density was low at 140,000/㎤, the surface roughness (Ra) was poor at 2.1 ㎛, and the formability was poor.

In the case of Comparative Example 2, the nucleating agent content was too low at 1 part by weight, so the cell density was low at 130,000/cm3, the surface roughness (Ra) was poor at 2.3 ㎛, and the formability was poor.

Claims (8)

A foam sheet comprising a skin layer formed to a depth of 150 ㎛ from the surface,
The cell density of the foam sheet is more than 160,000/cm3.
The surface roughness (Ra) of the skin layer is 2 ㎛ or less,
The foam sheet is formed from a composition comprising 3 to 4 parts by weight of a thickener, 1.5 to 5 parts by weight of a nucleating agent, and 2 to 4 parts by weight of a foaming agent, per 100 parts by weight of the resin.
The intrinsic viscosity (IV) of the composition is 0.9 to 1 ㎗/g,
Foam sheet having a skin layer density of 500 kg/㎥ or more. delete delete delete In the first paragraph,
A foam sheet having a cell size of 200 to 400 ㎛ in the core layer, which is an area excluding the skin layer among the foam sheets. Automobile interior material made from a foam sheet according to Article 1. In Article 6,
An automotive interior material made of a single composite polyethylene terephthalate (PET) material comprising a PET nonwoven fabric laminated on one or both sides of a foam sheet. In Article 6,
Automobile interior material having a three-dimensional shape with a depth of 10 cm or more.