KR20200087295A - Foam sheet having excellent cell expression uniformity, and preparation method thereof - Google Patents

Abstract

A foam sheet according to the present invention is composed of a polyester resin, and thus is cost competitive, safe for the human body, and eco-friendly. In addition, the foam sheet has advantages of having excellent impact resistance and moldability, and having high cell expression uniformity due to uniform dispersion of inorganic particles of a specific size in the polyester resin, and is advantageous in that cell size can be adjusted according to the size of the inorganic particles.

Description

Foam sheet having excellent cell expression uniformity, and preparation method thereof

The present invention relates to a foam sheet excellent in cell expression uniformity including inorganic particles and a method for manufacturing the same.

Products used as disposable food containers are divided into foamed and non-foamed products. In general, the foamed container is a product in which polystyrene is mixed with foamed gas to be extruded. The foamed container can maintain a relatively thick thickness, so it has advantages of maintaining shape, insulation, and price competitiveness, but is harmful to humans at high temperatures. There is a problem that is released. In addition, in the case of a non-foaming type container, a product made of heat-stable polypropylene in a film form is used, but the non-foaming type container has a small form change rate at high temperature and no harmful substances are detected, but the price is expensive and the problem of poor insulation have.

A cup ramen container is a representative product that uses a disposable heat-resistant container the most. As the cup ramen container, the aforementioned polystyrene foam container is generally used, and efforts to replace it with a paper container have been attempted. However, in the case of paper containers, there is a limit to commercialization because the manufacturing cost is high and the price competitiveness is low.

On the other hand, with the recent increase in the number of single-person households, the demand for delivery food and convenience food products is gradually increasing, and the need for disposable containers that are economical and safe from harmful substances is gradually increasing.

Accordingly, there is a need to develop a disposable container that is excellent in shape retention and heat insulation, and has an excellent aesthetic effect due to easy appearance design, and is competitive in price and safe for the human body.

Republic of Korea Patent Publication No. 2012-0058347

Accordingly, an object of the present invention is to provide a material for an excellent disposable container, which is excellent in shape retention and heat insulation, has a competitive price, and is safe for the human body.

The present invention in one embodiment,

As a foam sheet of a polyester resin containing inorganic particles,

The average size of the inorganic particles is 0.05 μm to 60 μm,

The average cell size of the foam sheet is 5 μm to 500 μm,

A foam sheet satisfying Equation 1 below is provided:

[Equation 1]

50% = |V ₁ -V ₀ | / V ₀ × 100 = 300%

In Equation 1,

V ₀ is the volume of the foam sheet before exposing the circular foam sheet having a diameter of 10 cm in a 200° C. oven for 30 seconds, the unit is cm ³ ,

V ₁ is the volume of the foam sheet, and the unit is cm ³ after exposing the circular foam sheet having a diameter of 10 cm in an oven at 200° C. for 30 seconds.

In addition, the present invention in one embodiment,

As a food container comprising the foam sheet, a food container satisfying Equation 3 below is provided:

[Equation 3]

|CV ₁ -CV ₀ | / CV ₀ × 100 = 15%

In Equation 3,

CV ₀ is the volume of the foam sheet before exposing the food container in a 200° C. oven for 30 seconds, the unit is cm ³ ,

CV ₁ is the volume of the foam sheet after exposure of the food container in an oven at 200° C. for 30 seconds, and the unit is cm ³ .

Furthermore, the present invention is in one embodiment,

A step of preparing a foam sheet by extrusion foaming a resin mixture containing a polyester resin and inorganic particles,

The average size of the inorganic particles is 0.05 μm to 60 μm,

The average cell size of the foam sheet provides a method for producing a foam sheet of 5 μm to 500 μm.

The foam sheet according to the present invention is made of polyester resin, and is competitive in price, safe for the human body, and environmentally friendly. In addition, the foamed sheet has excellent impact resistance and moldability, and uniformly disperses inorganic particles of a specific size in a polyester resin to increase the uniformity of cell expression of the foamed sheet, and can adjust the cell size according to the size of the inorganic particles. There is an advantage.

1 is an image taken by a scanning electron microscope (SEM) for the Examples and Comparative Examples.

The present invention relates to a foam sheet and a method for manufacturing the same.

Recently, attempts have been made to develop a foamed container using polyester to replace the foamed container using polystyrene or a non-foamed container using polypropylene. However, when a polyester, especially polyethylene terephthalate (PET) is made of a foam sheet, it induces foaming while introducing a nucleating agent masterbatch, but when a separate nucleating agent is added, the added nucleating agent lacks dispersibility. Accordingly, the uniformity of the expressed cells may be deteriorated, and content unevenness may occur due to process errors. In addition, the conventional PET foam sheet has a problem that the melting point is lower than that of the polystyrene foam sheet, so that it is difficult to mold under the molding temperature conditions of polystyrene.

To improve this problem, the present invention provides a foam sheet comprising a polyester resin and a method for manufacturing the same.

The foam sheet according to the present invention is made of polyester resin, and is competitive in price, safe for the human body, and environmentally friendly. In addition, the foamed sheet has excellent impact resistance and moldability, and uniformly disperses inorganic particles of a specific size inside the polyester resin, resulting in high cell expression uniformity of the foamed sheet, and the cell size according to the size of the inorganic particles during foaming. It has the advantage of being adjustable.

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

Foam sheet

The present invention, in one embodiment, as a foam sheet of a polyester resin containing inorganic particles,

The average size of the inorganic particles is 0.05 μm to 60 μm,

The average cell size of the foam sheet is 5 μm to 500 μm,

A foam sheet satisfying Equation 1 below is provided:

[Equation 1]

50% = |V ₁ -V ₀ | / V ₀ × 100 = 300%

In Equation 1,

V ₀ is the volume of the foam sheet before exposing the circular foam sheet having a diameter of 10 cm in a 200° C. oven for 30 seconds, the unit is cm ³ ,

V ₁ is the volume of the foam sheet, and the unit is cm ³ after exposing the circular foam sheet having a diameter of 10 cm in an oven at 200° C. for 30 seconds.

The foam sheet according to the present invention is a foam sheet comprising a polyester resin as a main component, and may have a structure in which inorganic particles are uniformly dispersed inside a layer composed of the polyester resin.

At this time, the inorganic particles may be included in an amount of 0.05% to 1.00% by weight relative to the total weight of the foam sheet, and more specifically, 0.05% to 0.80% by weight, 0.05% to 0.60% by weight, based on the total weight of the foam sheet, 0.05 wt% to 0.40 wt%, 0.10 wt% to 0.50 wt%, 0.15 wt% to 0.45 wt%, or 0.20 wt% to 0.40 wt%.

In addition, the inorganic particles may be at least one selected from the group consisting of titanium oxide (TiO ₂ ), talc (Talc), silica (silica), and zirconium oxide (ZrO ₂ ). As an example, the inorganic particles may be titanium oxide (TiO ₂ ), talc (Talc) or silica (silica). The inorganic particles may serve to increase the density of the cell while reducing the cell size when foaming the polyester resin.

In addition, the size of the inorganic particles may be 0.05 ㎛ to 60 ㎛, specifically 0.05 ㎛ to 50 ㎛, 0.05 ㎛ to 40 ㎛, 0.05 ㎛ to 30 ㎛, 0.05 ㎛ to 20 ㎛, 0.05 ㎛ to 15 ㎛, 0.05 μm to 5 μm, 0.05 μm to 1 μm, 0.05 μm to 0.6 μm, 0.05 μm to 0.2 μm, 0.15 μm to 0.6 μm, 0.4 μm to 6 μm, 0.4 μm to 11 μm, 0.08 μm to 40 μm, 0.1 μm To 35 μm, 1 μm to 15 μm, 1 μm to 9 μm, 1 μm to 5 μm, 8 μm to 20 μm, 8 μm to 15 μm¸8 μm to 12 μm, 12 μm to 25 μm, 18 μm to 30 μm Μm, 20 μm to 40 μm, 35 μm to 60 μm, 45 μm to 60 μm, or 45 μm to 55 μm. According to the present invention, the foaming property and cell size of a cell can be easily controlled when the polyester resin is foamed by controlling the size of the inorganic particles within the above range. For example, the inorganic particles may be uniformly dispersed in the polyester resin to maintain the foamability of the resin constant, thereby uniformizing the cell uniformity of the extruded sheet, that is, the cell size dispersion. In addition, as the size of the inorganic particles uniformly dispersed in the polyester resin decreases, the size of the cell decreases, thereby increasing the density of the cell.

For example, the average cell size of the foam sheet may be 5 μm to 500 μm, specifically 10 μm to 400 μm, 15 μm to 450 μm, 20 μm to 400 μm, 50 μm to 370 μm, 15 μm to 200 μm, 80 μm to 350 μm, 100 μm to 300 μm, 70 μm to 120 μm, 30 μm to 110 μm, 250 μm to 370 μm, 290 μm to 410 μm, 280 μm to 320 μm, 330 μm to 380 μm , 5 μm to 50 μm or 5 μm to 30 μm.

In addition, the cell size of the foam sheet is excellent in uniformity (or uniformity in expression), so the average cell size and the deviation between the maximum and minimum cell sizes may be low. Specifically, in the foam sheet of the present invention, the maximum and minimum cell sizes may be within ±65%, within ±60%, within ±50%, or within ±45% based on the average cell size. As an example, when the average cell size of the foam sheet is 10 μm, the maximum cell size may be 15 μm or less, the minimum cell size may be 5 μm or more, and when the average cell size is 350 μm, the maximum cell size is 500 μm. Below, the minimum cell size may be 200 μm or more.

Furthermore, the average cell density of the foam sheet may be 800 cells/cm 2 to 25000 cells/cm 2, specifically 800 cells/cm 2 to 23000 cells/cm 2, 800 cells/cm 2 to 20000 cells/cm 2, 800 cells/cm 2 to 15000 cells/cm2, 800 cells/cm2 to 11000 cells/cm2, 800 cells/cm2 to 8000 cells/cm2, 1000 cells/cm2 to 5500 cells/cm2, 4500 cells/cm2 to 6000 cells/cm2, 15000 cells/cm2 to 25000 cells/cm2, 20000 cells/cm2 to 24500 cells/cm2, 21000 cells/cm2 to 24500 cells/cm2, 900 cells/cm2 to 2000 cells/cm2, 900 cells/cm2 to 1800 cells/cm2, or 1200 cells/cm2 To 1600 cells/cm 2.

In addition, the foam sheet satisfies Equation 1:

[Equation 1]

50% = |V ₁ -V ₀ | / V ₀ × 100 = 300%

In Equation 1,

V ₀ is the volume of the foam sheet before exposing the circular foam sheet having a diameter of 10 cm in a 200° C. oven for 30 seconds, the unit is cm ³ ,

V ₁ is the volume of the foam sheet, and the unit is cm ³ after exposing the circular foam sheet having a diameter of 10 cm in an oven at 200° C. for 30 seconds.

Specifically, in the foam sheet of the present invention, when the volume change is evaluated by measuring the dimensional change rate of the diameter and thickness before and after exposure to an oven at 200° C. for 30 seconds, the dimensional change rate according to Equation 1 is 50 to 280%, 50 To 250%, 50 to 200%, 50 to 150%, 50 to 100%, 50 to 90%, 50 to 80%, 50 to 70%, 100 to 300%, 150 to 300%, 200 to 300%, 250 To 300%, 80 to 120%, 80 to 140%, 150 to 200%, 180 to 300%, 220 to 290%, 270 to 300%, 90 to 150%, 90 to 160%, 110 to 170%, 130 To 170%, 140 to 160%, 140 to 190%, 190 to 2430%, 170 to 210%, 190 to 210%, 220 to 280%, 240 to 260%, or 230 to 280%.

In addition, the foamed sheet exhibits a high average cell density, so that impact resistance suitable for food containers or food and beverage containers can be realized. As one example, the foam sheet according to the present invention is excellent in impact resistance, so that the condition of Equation 2 below may be satisfied:

[Equation 2]

|SV ₁ -SV ₀ | / SV ₀ × 100 = 20%

In Equation 2,

SV ₀ is the volume of the foam sheet before the free fall of a sphere (diameter: 7 cm) of 500 g at a position of 30 cm in height from a foam sheet having a length of 10 cm and a width of 10 cm, the unit is cm ³ ,

SV ₁ is the volume of the foam sheet, and the unit is cm ³ , after freely falling 500 g spheres (diameter: 7 cm) from the foam sheet having a length of 10 cm and a width of 10 cm to a foam sheet at a position of 30 cm in height.

The rate of shape change according to Equation 2 is a value corresponding to the case where the foam sheet is impacted from the outside, and the volume means a value calculated by multiplying each length, width, and thickness of the foam sheet. The foam sheet according to the present invention (average thickness: 2.5 mm) is cut into 10 cm in length and 10 cm in width, and then frees a sphere of 500 g (diameter: 7 cm) from the foam sheet to a height of 30 cm with a foam sheet. When falling, the rate of change of the shape of the foam sheet according to Equation 2 may range from 0.01 to 20%, 0.05 to 18%, 0.1 to 15%, 0.1 to 10%, or 0.1 to 5%, and in some cases 0% Can be close to The foam sheet of the present invention has improved impact resistance by satisfying Equation (2), and thus, when subjected to an impact from the outside, deformation may not occur or may have a significantly lower form strain.

Furthermore, the foam sheet may further include carbon black together with inorganic particles in the polyester resin. At this time, the content of the carbon black may be 0.05% to 5% by weight relative to the total weight of the foam sheet, specifically 0.05% to 4.5% by weight, 0.05 to 3.5% by weight, 0.05% to 2.5% by weight, 0.05% to 1.5%, 0.05% to 0.6%, 0.05% to 0.2%, 0.4% to 3.5%, 0.4% to 2.5%, 0.4% to 1.5%, 0.8% % To 3.5 wt%, 0.8 wt% to 2.5 wt%, 0.8 wt% to 1.5 wt%, 0.8 wt% to 1.2 wt%, 1.2 wt% to 2.5 wt%, 1.8 wt% to 2.2 wt%, 2.2 wt% to It may be 3.2 wt%, 2.3 wt% to 2.8 wt%, 2.7 wt% to 3.3 wt%, 0.3 to 3.1 wt%, 0.2 to 0.8 wt% or 0.15 wt% to 3.5 wt%.

In addition, the average size of the carbon black may be 10 nm to 5000 nm, more specifically 20 nm to 3500 nm, 20 nm to 2500 nm, 20 nm to 2000 nm, 20 nm to 1500 nm, 20 nm to 1000 Nm, 20 nm to 800 nm, 20 nm to 400 nm, 20 nm to 200 nm, 20 nm to 80 nm, 20 nm to 50 nm, 80 nm to 3500 nm, 80 nm to 2500 nm, 100 nm to 1000 nm, It may be 80 nm to 130 nm, 400 nm to 600 nm, 450 nm to 550 nm, 800 nm to 1200 nm, 1000 nm to 3000 nm, 15 nm to 200 nm or 25 nm to 550 nm.

For example, the polyester resin of the present invention may include carbon black having an average size of 25 nm to 35 nm at 1±0.5% by weight based on the total weight of the foam sheet.

The present invention can control the average size and content of carbon black in the polyester resin within the above range, thereby simultaneously improving the thermal properties and moldability of the foam sheet containing the polyester resin, thereby shortening the process time during molding.

In addition, the foam sheet according to the present invention may exhibit a certain value when measuring a specific resistance value. Specifically, the foam sheet may have an average specific resistance value of 10 ⁷ to 10 ¹⁴ , and more specifically, 10 ⁷ to 10 ¹³ , 5×10 ⁷ to 10 ¹³ , 5×10 ⁷ to 5×10 ¹² , 10 ⁸ to 10 ¹² , or 10 ⁹ to 10 ¹² may have an average specific resistance value.

On the other hand, the foam sheet according to the present invention is a polyester resin foam sheet as described above, the polyester resin is advantageous in that it not only does not release substances harmful to the human body even at high temperatures, and is competitive in price.

Examples of such polyester resins include aromatic and aliphatic polyester resins in which a dicarboxylic acid component and a glycol component are polymerized or synthesized from hydroxycarboxylic acid. For example, the polyester resin is polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (Polytrimethylene Terephthalate, PTT), polyethylene naphthalate (Polyethylene naphthalate, PEN), polyethylene adipate (Polyehtylene adipate, PEA), poly lactic acid (Poly Lactic acid, PLA), and polyglycolic acid (Polyglycolic acid, PGA) may include one or more selected from the group consisting of, specifically, May include polyethylene terephthalate (PET).

In addition, the average thickness of the foam sheet of the present invention may be 1 mm to 10 mm. Specifically, the thickness of the foam sheet may be 1.5 mm to 9.0 mm, 2.0 mm to 8.0 mm, 1.5 mm to 5.0 mm or 2.0 mm to 7.0 mm.

Food container

In addition, the present invention in one embodiment,

A food container comprising the foam sheet and satisfying Equation 3 below is provided:

[Equation 3]

|CV ₁ -CV ₀ | / CV ₀ × 100 = 15%

In Equation 3,

CV ₀ is the volume of the foam sheet before exposing the food container in a 200° C. oven for 30 seconds, the unit is cm ³ ,

CV ₁ is the volume of the foam sheet after exposure of the food container in an oven at 200° C. for 30 seconds, and the unit is cm ³ .

The food container according to the present invention includes the foam sheet, and has excellent heat resistance, so that the volume change may be low even when exposed in an oven at 200° C. for 30 seconds.

Specifically, the rate of dimensional change before and after exposing the food container in an oven at 200° C. for 30 seconds was measured. This may correspond to a condition that may be encountered in environmental conditions using an actual food container or may be a dimensional change rate measured under more severe conditions, and the volume may be calculated by multiplying the length of each food container length, width, and thickness, for example. Value. The food container of the present invention may have a dimensional change rate according to Equation 3 in the range of 0.01 to 5%, 0.01 to 3%, or 0.01 to 1%. By satisfying the value of Equation 3 in the above range, it can be seen that the foam sheet according to the present invention hardly undergoes a morphological change even in use in a high temperature environment. As a result, it can be seen that the food container according to the present invention has excellent heat resistance.

Manufacturing method of foam sheet

Furthermore, the present invention is in one embodiment,

It comprises the step of preparing a foam sheet by extrusion foaming a resin mixture containing a polyester resin and inorganic particles,

The average size of the inorganic particles is 0.05 μm to 60 μm,

The average cell size of the foam sheet provides a method for producing a foam sheet of 5 μm to 500 μm.

The method of manufacturing a foam sheet according to the present invention can uniformly mix inorganic particles having a specific size in a polyester resin during extrusion foaming, thereby increasing the cell expression uniformity of the foam sheet and controlling the cell size to be smaller.

At this time, the polyester resin may be prepared from raw material components commonly used in the art. Specifically, the polyester resin may be obtained by reacting a dicarboxylic acid component and a glycol component or reacting a hydroxycarboxylic acid component.

Here, as the dicarboxylic acid component, one or more selected from the group consisting of terephthalic acid, naphthalene dicarboxylic acid and adipic acid may be used.

Also, as the glycol component, one or more selected from the group consisting of ethylene glycol, butylehe glycol, and propanediol may be used.

Further, the hydroxycarboxylic acid component may be used one or more selected from the group consisting of lactic acid and glycolic acid, but is not limited thereto.

As an example, the polyester resin used in the present invention may be polyethylene terephthalate (PET) obtained by reacting terephthalic acid with ethylene glycol.

In addition, the inorganic particles contained in the resin mixture may be at least one selected from the group consisting of titanium oxide (TiO ₂ ), talc, silica and zirconium oxide (ZrO ₂ ), and the total weight of the resin mixture It may be included in 0.05% by weight to 1.00% by weight. In addition, the average size of the inorganic particles may be 0.05 μm to 60 μm. The present invention can increase the cell uniformity of the foam sheet by incorporating the inorganic particles having the above-described configuration into the resin mixture, and the density of the cell while reducing the cell size according to the average size of the inorganic particles when foaming the polyester resin Can increase.

In addition, the resin mixture may further include carbon black together with inorganic particles. At this time, the content of the carbon black may be 0.05% to 5% by weight relative to the total weight of the resin mixture, specifically 0.05% to 4.5% by weight, 0.05 to 3.5% by weight, 0.05% to 2.5% by weight, 0.05% to 1.5%, 0.05% to 0.6%, 0.05% to 0.2%, 0.4% to 3.5%, 0.4% to 2.5%, 0.4% to 1.5%, 0.8% % To 3.5 wt%, 0.8 wt% to 2.5 wt%, 0.8 wt% to 1.5 wt%, 0.8 wt% to 1.2 wt%, 1.2 wt% to 2.5 wt%, 1.8 wt% to 2.2 wt%, 2.2 wt% to It may be 3.2 wt%, 2.3 wt% to 2.8 wt%, 2.7 wt% to 3.3 wt%, 0.3 to 3.1 wt%, 0.2 to 0.8 wt% or 0.15 wt% to 3.5 wt%.

In addition, the average size of the carbon black may be 10 nm to 5000 nm, more specifically 20 nm to 3500 nm, 20 nm to 2500 nm, 20 nm to 2000 nm, 20 nm to 1500 nm, 20 nm to 1000 nm, 20 nm to 800 nm, 20 nm to 400 nm, 20 nm to 200 nm, 20 nm to 80 nm, 20 nm to 50 nm, 80 nm to 3500 nm, 80 nm to 2500 nm, 100 nm to 1000 nm , 80 nm to 130 nm, 400 nm to 600 nm, 450 nm to 550 nm, 800 nm to 1200 nm, 1000 nm to 3000 nm, 15 nm to 200 nm or 25 nm to 550 nm.

The present invention can uniformly mix the carbon black with the resin mixture during extrusion foaming of the resin mixture, thereby simultaneously improving the thermal properties and moldability of the foam sheet, and shorten the process time.

Meanwhile, the polyester resin may be introduced in the form of pellets, granules, beads, chips, powders, etc., and in some cases, introduced in a molten state. It might be.

As an example, the polyester resin may be introduced into an extruder in the form of a chip and extruded and foamed. In this case, the resin chip is melted at a temperature of 260°C to 300°C for melting of the resin chip. It can go through the melting process.

In addition, in the step of manufacturing the foam sheet, various types of additives may be introduced into the fluid connection line or the foaming process as necessary when introducing an extruder of polyester resin for functionalization of the foam sheet.

Specifically, the additives can impart barrier performance, hydrophilicity, or waterproofing function to the foam sheet, thickener, surfactant, hydrophilizing agent, heat stabilizer, waterproofing agent, cell size expander, infrared attenuator, plasticizer, It may include one or more selected from the group consisting of fire retardant chemicals, pigments, elastomers, extrusion aids, antioxidants, nucleating agents, static inhibitors and UV absorbers.

As one example, the method for manufacturing a foam sheet of the present invention may input one or more of a thickener, a nucleating agent, a heat stabilizer, and a foaming agent, and may further include one or more of the functional additives listed above.

Here, the thickener is not particularly limited, but in the present invention, for example, pyromellitic dianhydride (PMDA) may be used.

In addition, the thermal stabilizer may be an organic or inorganic phosphorus compound. The organic or inorganic phosphorus compound may be, for example, phosphoric acid and its organic esters, phosphorous acid and its organic esters. For example, the thermal stabilizer is a commercially available material, and may be phosphoric acid, alkyl phosphate, or aryl phosphate, and more specifically, triphenyl phosphate, but is not limited thereto.

In addition, examples of the foaming agent, nitrogen (N ₂ ), carbon dioxide (CO ₂ ), freon, butane, pentane, neopentane, hexane, isohexane, heptane, isoheptane, physical blowing agent such as methyl chloride, or azodicarbon Azodicarbonamide-based compound, p,p'-oxybis(benzenesulfonyl hydrazide)-based compound, N,N'-dinitrosopentamethylenetetra Chemical blowing agents such as amine (N,N'-dinitroso pentamethylene tetramine)-based compounds, and specifically, carbon dioxide (CO ₂ ) may be used in the present invention.

In addition, the extrusion performed in the present invention can be performed using various types of extruders. The foaming process can usually be carried out via bead foaming or extrusion foaming, but extrusion foaming is preferred in the present invention. Extrusion foaming can extrude and foam the resin mixture continuously, simplifying the process steps, enabling mass production, and preventing cracking and granular fracture between beads during foam expansion, thus providing better flexural strength and compression. Strength can be achieved.

In addition, the foam sheet prepared in the present invention may be a foam board and / or foam sheet, the average thickness is 1㎜ to 10㎜, 1.5㎜ to 9.0㎜, 2.0㎜ to 8.0㎜, 1.5㎜ to 5.0㎜ or 2㎜ It may be from 7.0 mm.

Hereinafter, the present invention will be described in more detail by examples and experimental examples.

However, the following examples and experimental examples are merely illustrative of the present invention, and the contents of the present invention are not limited to the following examples and experimental examples.

Example One.

Terephthalic acid and ethylene glycol were added to the ester reaction tank, and a typical polymerization reaction was performed at 258°C to prepare a polyethylene terephthalate polymer (PET oligomer) having a reaction rate of about 96%. 2-Methyl-1,3-propanediol (MPD) was mixed with the prepared polyetherine terephthalate (PET) to 2 mol% (unit fraction of ethylene glycol: 98 mol%), and an esterification reaction catalyst was added. The esterification reaction was performed at 250±2°C. Thereafter, a condensation polymerization reaction catalyst was added to the obtained reaction mixture, and the final temperature in the reaction vessel was adjusted to be 280±2° C. and 0.1 mmHg, respectively, to thereby perform a condensation polymerization reaction to prepare a copolymerized polyester resin.

0.5 parts by weight of pyromellitic dianhydride based on 100 parts by weight of the prepared polyester resin; 0.3 parts by weight of talc having an average size of 0.1 μm; And Irganox (IRG 1010) 0.1 parts by weight of the mixture, and heated to 280 ℃ to prepare a resin mixture. Then, as the blowing agent in the first extruder, butane (Butane) was added 3 parts by weight based on 100 parts by weight of the polyester resin, followed by extrusion foaming to prepare a polyester resin foam sheet having an average thickness of 2±0.5 mm.

Example 2 to 5.

A foam sheet was prepared in the same manner as in Example 1, except that the average size of the inorganic particles, talc, was adjusted as shown in Table 1 below.

Average particle size Example 2 0.5 μm Example 3 3 μm Example 4 10 μm Example 5 50 μm

Example 6

The same method as in Example 1, except that talc having an average size of 0.1 µm and carbon black having an average size of 30 nm as inorganic particles were added in an amount of 0.3 parts by weight and 0.1 parts by weight, respectively, based on 100 parts by weight of the polyester resin. To prepare a polyester resin foam sheet having an average thickness of 2±0.5mm.

Example 7 to 14.

A foam sheet was prepared in the same manner as in Example 6, except that the average size and content of the inorganic particles talc and carbon black were adjusted as shown in Table 2 below.

Inorganic particles Carbon black Kinds content Average size content Average size Example 7 Talc 0.3 wt% 3 μm 0.5 wt% 30±5 nm Example 8 1.0 wt% 30±5 nm Example 9 1.0 wt% 100±10 nm Example 10 1.0 wt% 500±50 nm Example 11 1.0 wt% 2000±500 nm Example 12 2.0 wt% 30±5 nm Example 13 3.0 wt% 30±5 nm Example 14 Silica 3.0 wt% 30±5 nm

Comparative example One.

Foaming of a polyester resin having an average thickness of 2±0.5 mm was performed in the same manner as in Example 1, except that talc having an average size of 100 μm as inorganic particles was added to 0.3 parts by weight based on 100 parts by weight of the polyester resin. Sheets were prepared.

Experimental Example .

In order to confirm the physical properties of the foam sheet according to the present invention, the following experiment was performed.

1) Cell size and density evaluation

Scanning electron microscopy (SEM) was performed on the foam sheets prepared in Examples 1 to 5 and Comparative Example 1, and the number of cells was counted within a certain unit area from the photographed image, and the unit area (horizontal 1 cm X height 1 cm) to evaluate the average cell density. In addition, in order to evaluate the cell expression uniformity, the maximum and minimum cell sizes among the expressed cells were measured, and the uniformity was evaluated by calculating the variation ratios of the measured maximum and minimum cell sizes and the average cell size. The results are shown in Figure 1 and Table 3.

division Comparative Example 1 Example 1 Example 2 Example 3 Example 4 Example 5 Average particle size 100 μm 0.1 μm 0.5 μm 3 μm 10 μm 50 μm Average cell size 700 μm 10 μm 20 μm 300 μm 350 μm 100 μm Cell
Manifestation
Uniformity Minimum cell size ≥200 ㎛ ≥5 μm ≥10 ㎛ ≥200 ㎛ ≥200 ㎛ ≥50 ㎛ Max cell size ≤1100 ㎛ ≤15 μm ≤30 μm ≤400 ㎛ ≤500 ㎛ ≤150 ㎛ Deviation rate based on average cell size ±71.4% ±50% ±50% ±50% ±42.8% ±50% Average cell density 768 cells/cm ² 24000 cells/cm ² 22300 cells/cm ² 1496 cells/cm ² 1520 cells/cm ² 5200 cells/cm ²

1 is an image taken with a scanning electron microscope (SEM) of the foam sheet obtained in Examples 1 to 5 and Comparative Example 1, (a) to (e) of FIG. 1 are sequentially foamed in Examples 1 to 5 The sheet is an image taken with a scanning electron microscope, and FIG. 1(f) is an image taken with the foam sheet of Comparative Example 1. Referring to Figure 1, it can be seen that the cell size of the foam sheet of Examples 1 to 5 is significantly smaller than the average cell size of the foam sheet of Comparative Example 1, and the cell expression uniformity is uniform. More specifically, referring to Table 3, it was confirmed that the foam sheets of Examples 1 to 5 had an average cell size of 10 μm to 350 μm, while the foam sheets of Comparative Example 1 had an average cell size of 700 μm. In addition, while the foamed sheets of Examples 1 to 5 had a cell density of 1496 cells/cm 2 to 24000 cells/cm 2, it was found that the foamed sheets of Comparative Example 1 had a low cell density of 768 cells/cm 2. . Furthermore, in the foam sheet of Examples 1 to 5, the maximum and minimum cell sizes were ±50% based on the average cell size, whereas the foam sheet of Comparative Example 1 had the maximum and minimum cell sizes ±70 based on the average cell size. % Or higher.

This is because the foam sheet of the embodiment contains inorganic particles of a certain size and is similar to the comparative example or contains a small amount of inorganic particles in the polyester resin to be more uniformly dispersed to form relatively small size cells with high uniformity. Means

2) Impact resistance evaluation

Further, the foam sheets prepared in Examples 1 to 5 and Comparative Example 1 were cut into lengths of 10 cm, widths of 10 cm, and thicknesses of 2.5 cm, respectively, and 500 g spheres (diameter: 7) at a position of 30 cm in height from the foam sheets. cm) was freely dropped, and then the volume change of the foam sheet was measured to derive the morphology. At this time, the shape strain was set to 100% of the volume before the free fall of the sphere, the volume change after the free fall was set to the shape strain, and the maintained volume was made into impact resistance, and the results are shown in Table 4.

division Comparative Example 1 Example 1 Example 2 Example 3 Example 4 Example 5 Average particle size 100 μm 0.1 μm 0.5 μm 3 μm 10 μm 50 μm Cell size 700 μm 10 μm 20 μm 300 μm 350 μm 100 μm Cell density 768 cells/cm ² 24000 cells/cm ² 22300 cells/cm ² 1496 cells/cm ² 1520 cells/cm ² 5200 cells/cm ² Impact resistance 80% 97% 96.4% 92.5% 90% 93% Shape strain 20% 3% 3.6% 7.5% 10% 7%

Looking at Table 4, as a result of the impact resistance test, the foam sheet of Examples 1 to 5 had a morphology of 3% to 10%, while the foam sheet of Comparative Example 1 showed a morphology of more than 15%. This indicates that the impact resistance of the foamed sheet is dependent on the size and density of the cell. In the foamed sheet of the present invention, when the resin constituting the foamed sheet is mixed with inorganic particles, the cell uniformity and size are controlled to increase the cell density. It can be seen that, accordingly, the impact resistance of the foam sheet is improved.

3) Evaluation of electrical properties

The specific sheet was measured for the foam sheets obtained in Examples 6 to 14 and Comparative Example 1. Specifically, the foam sheet was cut into widths of 25 cm and length of 25 cm, and the surface resistivity meter (PRS-801, Prostat) was used to measure the specific resistance value of the foam sheet surface at a temperature of 25°C and a relative humidity of 40%. It was measured and the average value was derived.

Then, under the same conditions, it was confirmed whether static electricity was generated on the surface of the foamed sheet with an electrostatic measuring device (Stat Clean Eye-02, VESSEL), and the measurement results are shown in Table 5.

division Comparative Example 2 Example 6 Example 7 Example 8 Example 9 Example 10 Example 11 Example 12 Example 13 Example 14 Inorganic particles
Kinds Talc Talc Silica Carbon black content
[weight%] 0 0.1 0.5 One One One One 2 3 3 Carbon black average size
[nm] - 30±5 30±5 30±5 100±10 500±50 2000±500 30±5 30±5 30±5 Foam sheet specific resistance value [Ω·㎝] 10 ¹⁵ 10 ¹² 10 ¹² 10 ¹² 10 ¹² 10 ¹² 10 ¹² 10 ¹⁰ 10 ⁸ 10 ⁸ Static electricity generation ○ X X X X X X X X X

Looking at Table 5, the foam sheet of Examples 6 to 14 has an average resistivity value of 10 ⁸ to 10 ¹² Ω·cm, and the specific resistance value decreases as the content of carbon black dispersed in the foam sheet increases. Was confirmed. On the other hand, it was confirmed that the foam sheet of Comparative Example 1 has a high specific resistance value of 10 ¹⁵ Ω·cm. In addition, the foam sheets of Examples 6 to 14 did not generate static electricity, but it was confirmed that the foam sheets of Comparative Example 1 generate static electricity. Through this, it can be seen that the foam sheets of Examples 6 to 14 have a relatively low specific resistance value and suppress the generation of static electricity by adding carbon black.

4) Evaluation of thermal properties

The foam sheets of Examples 6 to 14 and Comparative Example 1 were put into a pre-heater of a molding machine, and the time taken until the surface temperature of the foam sheet reached 180°C was measured to evaluate the sheet preheating time. .

Then, each foam sheet was molded into a mold at 200°C using a mold machine having a bent portion, and the molding state at the bent portion of the mold machine was visually evaluated. At this time, the molding state was evaluated by dividing it into three stages: excellent, normal, and bad.

Finally, the foam sheets (average thickness: 2.5 mm) of Examples 6 to 14 and Comparative Example 1 were cut into circles having a diameter of 10 cm, and the cut sheets were left in an oven at 200° C. for 30 seconds and then returned to room temperature. After cooling, the volume change was confirmed by measuring the diameter and thickness of the foam sheet. In addition, the foam sheet (average thickness: 2.5 mm) was molded into a mold to produce a cylindrical shaped article having a diameter of 15 cm and a height of 8 cm, and heat treatment under the same conditions (save in an oven at 200° C. for 30 seconds and cool to room temperature). The volume change was measured accordingly. The measured results are shown in Table 6.

division Comparative Example 1 Example 6 Example 7 Example 8 Example 9 Example 10 Example 11 Example 12 Example 13 Example 14 Inorganic particles
Kinds Talc Talc Silica Carbon black content
[weight%] 0 0.1 0.5 One One One One 2 3 3 Carbon black average size
[nm] - 30±5 30±5 30±5 100±10 500±50 2000±500 30±5 30±5 30±5 Sheet preheating time (sec) 20 10 10 10 10 10 10 8 6 6 Formability Bad usually usually Great Great Great Great Great Great Great Volume change
(%) firing
Sheet 40 100 150 200 200 200 200 250 250 150 Molded article 17 5 5 5 5 5 5 3 2 2

Referring to Table 6, in the foam sheet of Examples 6 to 14, the time for the surface temperature to reach 180° C. is less than 15 seconds, specifically, it takes 5 to 12 seconds, whereas the foam sheet of Comparative Example 1 has a time of 20 seconds or more. It was confirmed that it reached 180°C only after passing. This means that the foam sheet of the embodiment has a high thermal conductivity.

In addition, the foamed sheets of Examples 6 to 14 were excellent in moldability, so it was found that no breakage or crushing of the bend was found at the bent portion of the mold machine. However, it was confirmed that the foam sheet of Comparative Example 1 had low moldability and had cracks or crushes in the bent portions.

In addition, when the foam sheets of Examples 6 to 14 were left in an oven at 200° C. for 30 seconds, they exhibited a volume change of about 80 to 270%, and in the case of a molded article molded from the foam sheet, the volume change was 6 %. In comparison, the foam sheet of Comparative Example 1 exhibited a volume change of less than about 50% when left in an oven at 200° C. for 30 seconds, and the molded article molded from the foam sheet was significantly reduced with shrinkage of the foam sheet under the same conditions. A morphological change appeared, and it was confirmed that the volume change was 15% or more.

From these results, the foamed sheet according to the present invention has a high thermal conductivity, so the surface temperature of the foamed sheet rises rapidly, so that the moldability is excellent and the molding time is short, and the food container manufactured using this is excellent in heat resistance and molded at a high temperature. It can be seen that damage such as morphology change does not occur even in the case.

Claims (14)

As a foam sheet of a polyester resin containing inorganic particles,
The average size of the inorganic particles is 0.05 μm to 60 μm,
The average cell size of the foam sheet is 5 μm to 500 μm,
Foam sheet satisfying the following equation (1):
[Equation 1]
50% = |V ₁ -V ₀ | / V ₀ × 100 = 300%
In Equation 1,
V ₀ is the volume of the foam sheet before exposing the circular foam sheet having a diameter of 10 cm in a 200° C. oven for 30 seconds, the unit is cm ³ ,
V ₁ is the volume of the foam sheet, and the unit is cm ³ after exposing the circular foam sheet having a diameter of 10 cm in an oven at 200° C. for 30 seconds.
According to claim 1,
The foam sheet satisfies the following equation (2):
[Equation 2]
|SV ₁ -SV ₀ | / SV ₀ × 100 = 20%
In Equation 2,
SV ₀ is the volume of the foam sheet before the free fall of a sphere (diameter: 7 cm) of 500 g at a position of 30 cm in height from a foam sheet having a length of 10 cm and a width of 10 cm, the unit is cm ³ ,
SV ₁ is the volume of the foam sheet, and the unit is cm ³ , after freely falling 500 g spheres (diameter: 7 cm) from the foam sheet having a length of 10 cm and a width of 10 cm to a foam sheet at a position of 30 cm in height.
According to claim 1,
The content of the inorganic particles is 0.05% by weight to 1.00% by weight relative to the total weight of the foam sheet.
According to claim 1,
The inorganic particles are at least one foam sheet selected from the group consisting of titanium oxide (TiO ₂ ), talc, silica and zirconium oxide (ZrO ₂ ).
According to claim 1,
The foamed sheet has an average cell density of 800 cells/cm 2 to 25000 cells/cm 2.
According to claim 1,
Polyester resins include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN), and polyethylene adipate Foam sheet of at least one member selected from the group consisting of parts (Polyehtylene adipate, PEA), Poly Lactic acid (PLA), and Polyglycolic acid (PGA).
According to claim 1,
The polyester resin further includes carbon black,
The content of the carbon black foam sheet is 0.05% to 5% by weight relative to the total weight of the foam sheet.
The method of claim 6,
Carbon black foam sheet having an average size of 10 nm to 5000 nm.
A food container comprising the foam sheet according to claim 1,
Food container satisfying the following equation (3):
[Equation 3]
|CV ₁ -CV ₀ | / CV ₀ × 100 = 15%
In Equation 3,
CV ₀ is the volume of the foam sheet before exposing the food container in a 200° C. oven for 30 seconds, the unit is cm ³ ,
CV ₁ is the volume of the foam sheet after exposure of the food container in an oven at 200° C. for 30 seconds, and the unit is cm ³ .
It comprises the step of preparing a foam sheet by extrusion foaming a resin mixture containing a polyester resin and inorganic particles,
The average size of the inorganic particles is 0.05 μm to 60 μm,
The method of manufacturing a foam sheet having an average cell size of 5 μm to 500 μm.
The method of claim 10,
The polyester resin is polymerized from a dicarboxylic acid component and a glycol component; A method for producing a foam sheet produced by polymerizing a hydroxycarboxylic acid component.
The method of claim 10,
The step of manufacturing the foam sheet is a method of manufacturing the foam sheet to form a foam sheet with an average thickness of 1 mm to 10 mm.
The method of claim 10,
The content of the inorganic particles is 0.05 wt% to 1.00 wt% based on the total weight of the resin mixture.
The method of claim 10,
The resin mixture is a method of manufacturing a foam sheet further comprising 0.05% to 5% by weight of carbon black based on the total weight.

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