KR20240080366A - Electronic component thermal insulating material comprising material having reduced cell size - Google Patents

Abstract

The present invention relates to an electronic component insulation material using a material with a reduced cell size: a foam sheet having a thickness of 0.5 to 1.5 mm and a breakdown voltage of 3 kV or more.

Description

Electronic component thermal insulating material comprising material having reduced cell size}

The present invention relates to an electronic component insulation material using a material (foam sheet) with a reduced cell size.

Electronic components, such as those used in laptops, etc., operate by receiving power, so they need to have physical properties such as withstand voltage.

Therefore, the purpose of the present invention is to provide electronic components with excellent physical properties such as withstand voltage.

In order to achieve the above-mentioned object, the present invention provides a foam sheet having a thickness of 0.5 to 1.5 mm and a breakdown voltage of 3 kV or more.

The cell size of the foam sheet according to the present invention may be 400 ㎛ or less, and the density may be 500 kg/㎥ or less.

As for heat resistance of the foam sheet according to the present invention, the VICAT softening temperature may be 120°C or higher.

As for the impact resistance of the foam sheet according to the present invention, when a 500 g steel ball is dropped from a height of 1.3 m, the imprinted area can maintain more than 40% of the initial thickness.

The foam sheet according to the present invention may be a foam sheet that has been heat treated at a temperature of 150 to 250°C for 40 to 110 seconds.

The crystallinity of the foam sheet heat-treated according to the present invention may be 15% or more.

The foam sheet according to the present invention may be formed of a foam composition containing polyethylene terephthalate (PET) resin, a nucleating agent, and a thickener.

In the present invention, the intrinsic viscosity (IV) of the PET resin may be 0.7 dl/g or more.

In the present invention, the PET resin may be a PET resin in which the presence of molecules with a molecular weight of 10,000 or more, as expressed by differential molecular weight distribution, accounts for 60% by weight or more based on the total weight of the PET resin.

In the present invention, the size of the nucleating agent may be 10 ㎛ or less.

In the present invention, the content of the nucleating agent may be 1 to 10 parts by weight based on 100 parts by weight of PET resin.

In the present invention, the content of the thickener may be 0.3 to 10 parts by weight based on 100 parts by weight of PET resin.

The foam sheet according to the present invention can be used as an insulating material for electronic components.

The foam sheet according to the present invention can provide a foam sheet with a small cell size and low density by using the size and content of the nucleating agent, the content of the thickener, and the viscosity and molecular weight distribution of the resin within a specific range, thereby providing a low-density foam sheet with a small cell size. It is possible to provide electronic components with excellent physical properties such as strength, impact resistance, and heat resistance.

Hereinafter, the present invention will be described in detail.

The foam sheet according to the present invention is characterized by a thin thickness and a withstand voltage of 3 kV or more.

The thickness of the foam sheet may be 0.5 to 1.5 mm, 0.6 to 1.4 mm, 0.7 to 1.3 mm, 0.8 to 1.2 mm, or 0.9 to 1.1 mm.

The voltage resistance (ASTM D 149) of the foam sheet is the dielectric breakdown strength and may be 3 kV or more, 3.5 kV or more, 4 kV or more, 4.5 kV or more, 5 kV or more, 5.5 kV or more, or 6 kV or more. The upper limit of voltage resistance may be, for example, 10 kV or less, 9 kV or less, 8 kV or less, or 7 kV or less. The form of foam can develop voltage resistance.

The cell size of the foam sheet may be 400 ㎛ or less, 350 ㎛ or less, 300 ㎛ or less, 250 ㎛ or less, or 200 ㎛ or less. The lower limit for cell size may be, for example, 50 μm or greater, 80 μm or greater, or 100 μm or greater. Cell size may refer to the average cell size, and specifically, may refer to the average value of the major axis length and minor axis length of the cell. If the cell size is within the above range, impact resistance can be improved.

The density of the foam sheet may be 500 kg/m3 or less, 450 kg/m3 or less, 400 kg/m3 or less, or 350 kg/m3 or less. The lower limit of the density is, for example, 50 kg/m3 or more, 100 kg/m3. It may be more than 150 kg/m3, more than 200 kg/m3, more than 250 kg/m3, more than 300 kg/m3, or more than 350 kg/m3.

As for the heat resistance of the foam sheet (VICAT ISO 306 B50), the VICAT softening temperature may be 120°C or higher, 125°C or higher, 130°C or higher, 135°C or higher, or 140°C or higher. The upper limit value of the softening temperature may be, for example, 200°C or less, 190°C or less, 180°C or less, 170°C or less, 160°C or less, 150°C or less, or 145°C or less. For electronic product applications, a softening temperature in the above range is required.

As for the impact resistance (falling ball impact strength) of the foam sheet, when a 500 g steel ball is dropped from a height of 1.3 m, the imprinted area can maintain more than 40%, 45%, or 50% of the initial thickness. The upper limit of impact resistance may be, for example, 100% or less, 90% or less, 80% or less, 70% or less, or 60% or less. For example, if the initial thickness is 1 mm, the thickness of the notched area must be maintained at least 0.4 mm to satisfy impact resistance performance. In other words, if the initial thickness is 1 mm, the nick depth of the nicked area should not exceed 0.6 mm.

The surface roughness Ra of the foam sheet may be 2 ㎛ or less, 1.8 ㎛ or less, 1.6 ㎛ or less, or 1.4 ㎛ or less. The lower limit of the surface roughness Ra may be, for example, 0.5 μm or more, 0.8 μm or more, or 1 μm or more. The surface roughness may be centerline surface roughness.

The elongation of the foam sheet at 200°C and 60 seconds may be 300% or more, 350% or more, 400% or more, 450% or more, or 500% or more. The upper limit value of stretchability may be, for example, 700% or less, 650% or less, 600% or less, or 550% or less. Elongation at 200°C and 60 seconds may refer to the elongation measured after the sample was kept at 200°C for 60 seconds.

The maximum bending load of the foam sheet may be 5 N or more, 6 N or more, 7 N or more, 8 N or more, or 9 N or more. The upper limit of the maximum bending load may be, for example, 15 N or less, 14 N or less, 13 N or less, or 12 N or less.

The foam sheet may be a foam sheet that has been heat treated at a temperature of 150 to 250°C for 40 to 110 seconds. The heat treatment temperature may be 150 to 250°C, 160 to 240°C, 170 to 230°C, 180 to 220°C, or 190 to 210°C. The heat treatment time may be 40 to 110 seconds, 50 to 100 seconds, or 60 to 90 seconds. If the heat treatment time is short, crystallinity may decrease and heat resistance may deteriorate. Conversely, if the heat treatment time is long, impact resistance may decrease. Therefore, an appropriate heat treatment time within the above range is required.

The crystallinity of the heat-treated foam sheet may be 15% or higher, 16% or higher, 17% or higher, 18% or higher, 19% or higher, 20% or higher, 21 or higher, 22% or higher, or 23% or higher. The upper limit value of crystallinity may be, for example, 30% or less, 29% or less, 28% or less, 27% or less, 26% or less, 25% or less, or 24% or less. If the crystallinity is within the above range, the VICAT test can be passed.

The foam sheet may have closed cells. Having closed cells means that more than 90% of the cells of the foam sheet are closed cells (DIN ISO4590). For example, the percentage of closed cells in the foam sheet may be 90 to 100%, 95 to 100%, 97 to 100%, or 99 to 100%. By having a closed cell within this range, excellent lightness, durability, and rigidity can be satisfied.

The foam sheet may be formed of a foam composition containing polyethylene terephthalate (PET) resin, a nucleating agent, and a thickener. By using PET resin, it is environmentally friendly and can be easily reused.

The intrinsic viscosity (IV) of the PET resin may be greater than or equal to 0.7 dl/g, greater than or equal to 0.72 dl/g, greater than or equal to 0.74 dl/g, greater than or equal to 0.76 dl/g, greater than or equal to 0.78 dl/g, or greater than or equal to 0.8 dl/g. The upper limit value of intrinsic viscosity may be, for example, 1.0 dl/g, 0.95 dl/g, 0.9 dl/g, 0.85 dl/g, or 0.82 dl/g. Preferably, the intrinsic viscosity (IV) of the PET resin may be 0.76 to 0.82 dl/g. If the intrinsic viscosity is low, low-density foaming may be difficult, cell size and surface roughness may increase, and stretchability may be reduced.

The melting point of the PET resin may be 250°C or higher, 252°C or higher, 254°C or higher, or 256°C or higher. The upper limit of the melting point may be, for example, 300°C, 290°C, 280°C, 270°C, or 260°C.

The weight average molecular weight (Mw) of the PET resin may be 20,000 to 200,000, preferably 50,000 to 150,000, and more preferably 60,000 to 100,000. The weight average molecular weight can be measured by gel permeation chromatography (GPC, analysis equipment HLC-8320), and polymethyl methacrylate (PMMA) can be used as a standard sample. Molecular weight units can be g/mol or Da.

The PET resin may be a PET resin in which the presence of molecules with a molecular weight of 10,000 or more, expressed by differential molecular weight distribution, accounts for 60% by weight or more of the total weight of the PET resin. That is, the presence of molecules with a molecular weight of 10,000 or more in the PET resin may be 60% by weight or more, and the presence of molecules with a molecular weight of less than 10,000 may be less than 40% by weight. The presence ratio of molecules with a molecular weight of 10,000 or more may be preferably 65% by weight or more, and more preferably 70% by weight or more. The upper limit of the proportion of molecules with a molecular weight of 10,000 or more may be, for example, 100%, 95%, 90%, 85%, 80%, or 75%. If the presence ratio of molecules with a molecular weight of 10,000 or more is low, the maximum bending load may be reduced.

The differential molecular weight distribution uses the differential molecular weight distribution curve, which is one of the methods of expressing the molecular weight distribution of polymer substances. The differential molecular weight distribution curve is a curve that expresses the amount indicating how many grams of molecular weight M are in 1 g of a substance as a function of M.

Particularly preferably, the PET resin simultaneously satisfies the above physical properties, that is, has an intrinsic viscosity (IV) of 0.7 dl/g or more, a melting point of 250°C or more, a weight average molecular weight of 20,000 or more, and a differential molecular weight. It may be a PET resin in which the presence of molecules with a molecular weight of 10,000 or more, as indicated by distribution, accounts for 60% by weight or more of the total weight of the PET resin.

Nucleating agents are added to control cell size, such as talc, mica, silica, diatomaceous earth, alumina, titanium oxide, zinc oxide, magnesium oxide, magnesium hydroxide, aluminum hydroxide, calcium hydroxide, potassium carbonate, calcium carbonate. Inorganic compounds such as magnesium carbonate, potassium sulfate, barium sulfate, sodium bicarbonate, and glass beads can be used. Preferably, talc can be used as a nucleating agent.

The content of the nucleating agent may be 1 to 10 parts by weight, preferably 2 to 7 parts by weight, and more preferably 3 to 5 parts by weight, based on 100 parts by weight of PET resin. If the content of the nucleating agent is small, the cell size and surface roughness may increase and the maximum bending load and elongation may decrease.

The size of the nucleating agent may be 10 μm or less, 8 μm or less, 6 μm or less, 4 μm or less, or 3 μm or less. The lower limit on nucleating agent size may be, for example, at least 0.1 μm, at least 0.5 μm, or at least 1 μm. If the size of the nucleating agent is large, cell size and surface roughness may increase and stretchability may decrease. The size of the nucleating agent may mean the average size, and specifically may mean the average value of the major axis length and minor axis length of the nucleating agent.

The thickener is added to control the melt viscosity of the foaming composition, and for example, pyromellitic dianhydride (PMDA), epoxy, etc. can be used.

The content of the thickener may be 0.3 to 10 parts by weight, preferably 1 to 5 parts by weight, and more preferably 2 to 3 parts by weight, based on 100 parts by weight of PET resin. If the thickener content is low, foaming may not occur properly and density, cell size, and surface roughness may increase. In addition, melt strength can be secured within the above range and low density can be achieved.

The foaming agent is added to foam the composition and control the density of the foam sheet. For example, gases such as N ₂ , CO ₂ , and freon; Physical foaming agents such as butane, pentane, neopentane, hexane, isohexane, heptane, isoheptane, and methyl chloride; Chemical foaming agents such as azodicarbonamide-based compounds, P,P'-oxybis(benzenesulfonylhydrazide)-based compounds, and N,N'-dinitrosopentamethylenetetraamine-based compounds can be used.

The content of the foaming agent may be 0.1 to 5 parts by weight, preferably 0.5 to 4 parts by weight, and more preferably 1 to 3 parts by weight, based on 100 parts by weight of PET resin.

In addition, the raw materials of foam sheets are used for the purpose of providing hydrophilic function, waterproof function, flame retardant function, and ultraviolet ray blocking function, such as surfactant, UV blocker, hydrophilic agent, flame retardant, heat stabilizer, waterproofing agent, cell size expander, and infrared attenuation. It may further include agents, plasticizers, fire retardant chemicals, pigments, elastic polymers, extrusion aids, antioxidants, fillers, anti-slip agents, UV absorbers, etc.

The foam sheet can be formed through bead foaming or extrusion foaming. Bead foaming is a method of making a product by first foaming beads by heating them, maturing them for an appropriate period of time, filling them into plate-shaped or barrel-shaped molds, heating them again, and fusing and molding them through secondary foaming. Extrusion foaming simplifies the process steps by continuously extruding and foaming the resin melt, enables mass production, and achieves superior compressive strength by preventing cracks between beads and granular destruction during bead foaming. You can.

Preferably, the foam sheet can be manufactured using extrusion foam and a circular die. By extruding and foaming with a circular die, a foam sheet with smooth surfaces on both the upper and lower surfaces can be obtained.

On the other hand, when foam is extruded with a slit-shaped die, a board-type foam with a thickness of 5 mm or more is formed. When the foam board is cut to be 5 mm or less, at least one surface may not have a smooth surface because traces of cells being cut remain.

The method of manufacturing a foam sheet includes the steps of mixing PET resin, nucleating agent, thickener, foaming agent, etc. to produce a resin melt; And it may include extruding and foaming the resin melt with an extruder.

The step of preparing the resin melt may be performed at a temperature of 260 to 300°C. Additionally, PET resin may have the form of pellets, granules, beads, chips, etc., and in some cases, may be in the form of powder.

The extruding and foaming steps can be performed by cooling the foamable melt at 220 to 260° C. to facilitate foaming, and then passing the cooled foamable melt through a die. Additionally, the formed foam sheet can be cooled through a mandrel and an air ring to maintain the shape of the foam sheet. The foaming temperature may be 225 to 280°C, 225 to 275°C, or 225 to 265°C.

The foam sheet according to the present invention can be usefully used as an electronic component insulation material, electronic product cushioning material, etc.

As such, the foam sheet according to the present invention provides a foam sheet with a small cell size, low density, and thin thickness by using the size and content of the nucleating agent, the content of the thickener, and the viscosity and molecular weight distribution of the resin within a specific range. It is possible to provide electronic components with excellent physical properties such as withstand voltage, impact resistance, and heat resistance.

Hereinafter, the present invention will be described in more detail through examples.

[Examples and Comparative Examples]

Foam sheets for electronic components of Examples and Comparative Examples having the physical properties shown in Tables 1 and 2 were manufactured by extrusion foaming using the compositions shown in Tables 1 and 2.

The method of measuring each physical property is as follows.

(1) Intrinsic viscosity (IV)

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

(2) molecular weight

The molecular weight was measured at 254 nm by dissolving the sample in a mixed solution of chloroform and phenol (mixing ratio = 1:1 volume ratio) and using gel permeation chromatography (GPC, analysis equipment HLC-8320). The standard sample was PMMA.

(3) Density

Density was measured under KS M ISO 845 conditions.

(4) Cell size

The cell size was measured by measuring the length of the long and short axes of the cell using a scanning electron microscope (SEM), and the average value was taken as the cell size.

(5) Crystallinity

The melting enthalpy at the melting temperature and the crystallization enthalpy at the cooling crystallization temperature were measured using Differential Scanning Calorimetry (DSC), and the degree of crystallinity was calculated according to the formula below.

Crystallinity = ΔHm - ΔHc / ΔHm

ΔHm means enthalpy of melting, ΔHc means enthalpy of crystallization, and ΔHm means standard enthalpy of melting (140 J/g).

(6) Heat resistance

For heat resistance, the softening temperature was measured by conducting a VICAT test according to VICAT ISO 306 B50 and ASTM D 1525.

(7) Impact resistance

Impact resistance is measured by measuring the thickness of the notched area when a 500 g steel ball is dropped from a height of 1.3 m. If the thickness is more than 40% of the initial thickness (1 mm), it is judged as Pass, and if it is less than 40% or broken, it is judged as Fail. did. The horizontal number indicates the thickness of the stamped area.

(8) Voltage resistance

Voltage resistance was measured according to ASTM D 149, and when the breakdown strength was 3 kv or more, it was judged as Pass, and if it was less than 3 kv, it was judged as Fail. The number inside the horizontal indicates the dielectric breakdown strength.

division Example 1 Example 2 Example 3 Example 4 PET
profit Intrinsic viscosity (IV) ㎗/g 0.8 0.8 0.8 0.8 Molecular weight over 10,000 weight% 72 72 72 72 thickener PMDA weight part 2.5 2.5 2.5 2.5 nucleating agent Talc content weight part 3 3 3 3 talc size ㎛ One One One One blowing agent butane weight part One One 1.1 1.2 PET foam sheet density kg/㎥ 500 500 450 350 thickness mm One One One One average cell size ㎛ 100~200 100~200 100~200 100~200 Plate forming processing conditions heat treatment temperature ℃ 200 200 200 200 heat treatment time candle 60 90 60 60 crystallinity - % 17 23 16 15 heat resistance VICAT ISO 306 B50 ℃ 130 140 130 120 impact resistance 500g Steel Ball dropped from a height of 1.3m, dents over 0.4T mm Pass(0.5) Pass
(0.5) Pass
(0.5) Pass
(0.5) voltage resistance ASTM D 149, 3kV and above kV Pass (6) Pass (5.5) Pass (5.5) Pass (5.0)

division Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 PET
profit Intrinsic viscosity (IV) ㎗/g 0.8 Non-foaming
PET
Sheet 0.8 0.8 Molecular weight over 10,000 weight% 72 72 72 thickener PMDA weight part 2.5 2.5 2.5 nucleating agent Talc content weight part 3 3 3 talc size ㎛ 12 One One blowing agent butane weight part 2 2 2 PET foam sheet density kg/㎥ 500 500 500 thickness mm One One One average cell size ㎛ 400~600 100~200 100~200 Plate forming processing conditions heat treatment temperature ℃ 200 200 200 200 heat treatment time candle 60 60 30 120 crystallinity - % 17 17 13 25 heat resistance VICAT ISO 306 B50 ℃ 140 130 80 150 impact resistance 500g Steel Ball dropped from a height of 1.3m, dents over 0.4T mm Fail Pass
(0.6) Pass
(0.5) Fail
(fracture) voltage resistance ASTM D 149, 3kV and above kV Pass (6) Fail (2) Pass (6) Pass (6)

As can be seen from the table above, the foam sheet of the example had a small cell size and low density by using the size and content of the nucleating agent, the content of the thickener, and the viscosity and molecular weight distribution of the resin within an appropriate range. In addition, the composite material of the example had excellent heat resistance, impact resistance, and voltage resistance by using appropriate materials and heat treatment conditions.

However, in the case of Comparative Example 1, the size of the nucleating agent was large, the cell size increased, and the impact resistance decreased (impact strength was insufficient).

In the case of Comparative Example 2, the voltage resistance decreased because a non-foamed sheet was used.

In Comparative Example 3, the heat treatment time was short, so the crystallinity decreased and the heat resistance deteriorated.

In the case of Comparative Example 4, the heat treatment time was long, and the impact resistance decreased.

Claims (13)

A foam sheet with a thickness of 0.5 to 1.5 mm and a breakdown voltage of 3 kV or more. According to paragraph 1,
A foam sheet with a cell size of 400 ㎛ or less and a density of 500 kg/㎥ or less. According to paragraph 1,
VICAT foam sheet with a softening temperature of 120℃ or higher. According to paragraph 1,
A foam sheet that retains more than 40% of its initial thickness when a 500 g steel ball is dropped from a height of 1.3 m. According to paragraph 1,
The foam sheet is a foam sheet that is heat-treated at a temperature of 150 to 250 ° C. for 40 to 110 seconds. According to clause 5,
The heat-treated foam sheet has a crystallinity of 15% or more. According to paragraph 1,
A foam sheet is formed of a foam composition containing polyethylene terephthalate (PET) resin, a nucleating agent, and a thickener. In clause 7,
A foam sheet with an intrinsic viscosity (IV) of PET resin of 0.7 ㎗/g or more. In clause 7,
PET resin is a foam sheet made of PET resin in which the presence of molecules with a molecular weight of 10,000 or more, expressed by differential molecular weight distribution, accounts for more than 60% by weight of the total weight of the PET resin. In clause 7,
A foam sheet in which the size of the nucleating agent is 10 ㎛ or less. In clause 7,
The content of the nucleating agent is 1 to 10 parts by weight based on 100 parts by weight of PET resin. In clause 7,
The content of the thickener is 0.3 to 10 parts by weight based on 100 parts by weight of PET resin. According to paragraph 1,
Foam sheets are used as insulators for electronic components.