WO2021215701A1 - Polyester foam sheet having controlled carboxyl end group equivalent - Google Patents

Abstract

The present invention relates to a polyester foam sheet, 90% or greater of the cells of which are closed cells (DIN ISO 4590), the polyester foam sheet having carboxyl end group (CEG) equivalent of less than 100 meg/g and thus superb thermal plasticity.

Description

Polyester foam sheet with controlled equivalent of carboxyl end groups

The present invention relates to a polyester foam sheet in which the equivalent weight of carboxyl terminal groups is controlled, and a method for producing the same.

Polyester resins with crystallinity such as polyethylene terephthalate (PET) have superior mechanical properties compared to polyethylene-based resins or polypropylene-based resins, and have excellent heat resistance and chemical resistance, and are used in various fields requiring light weight and high physical properties. This is possible. Polyester resin has excellent mechanical and chemical properties, so it can be used for multi-purpose applications, for example, conventionally for drinking water containers and medical, food packaging, food containers, sheets, films, automobile molded products, etc. applications are being made in the field of

In particular, a foam sheet containing a polyester resin has a foaming layer composed of a resin composition containing a polyester resin, so it is excellent in light weight and strength, so that it can be used as a sheet-shaped molded article as it is, and three-dimensional such as thermoforming It can be molded into a molded body having a typical shape.

However, the foam sheet containing the polyester resin has the above-mentioned high rigidity, which is excellent in lightness and strength, so it is difficult to give a desired shape by thermoforming or the like, and there is a disadvantage in that it is easily broken. In addition, since a process such as thermoforming is included when a foam sheet is commercialized, the thermal properties of the polyester resin act as a very important factor.

An object of the present invention is to provide a polyester foam sheet in which the equivalent of a carboxyl end group (CEG, Carboxyl End Group) is controlled in order to solve the problems of the prior art as described above.

The polyester foam sheet according to an embodiment of the present invention is a polyester resin foam sheet in which 90% or more of cells are closed cells (DIN ISO4590), and the equivalent of carboxyl end groups (CEG, Carboxyl End Group) is 100 meq/g may be less than

In one embodiment, the polyester foam sheet, the foam sheet, has an average thickness of 1 to 10 mm, and an average density according to KS M ISO 845:2012 is in the range of ^{100 to 600 kg / m 3 .}

In a specific example, the polyester foam sheet satisfies Equation 1 below.

[Formula 1]

y = 0.0471x + 56.417

In Equation 1, y is the equivalent of the carboxyl terminal group of the polyester resin forming the foam sheet, and x is the density of the foam sheet.

In another specific example, the cell size of the foam sheet ranges from 100 to 700 μm on average.

For example, the polyester is polyethylene terephthalate (PET).

In one example, the foam sheet includes inorganic particles containing alkaline earth metal carbonate, and the content of the inorganic particles is in the range of 0.5 to 5% by weight.

In a specific example, the alkaline earth metal element is at least one selected from the group consisting of calcium (Ca), magnesium (Mg) and barium (Ba), and the average particle diameter of the inorganic particles is in the range of 1 to 5 μm.

Polyester foam sheet according to the present invention, by controlling the equivalent of a carboxyl end group (CEG, Carboxyl End Group) low, has a low dimensional change rate under high temperature conditions and excellent thermoformability characteristics of the foam sheet.

Since the present invention can have various changes and can have various forms, specific embodiments are illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to the specific disclosed form, it should be understood to include all modifications, equivalents and substitutes included in the spirit and scope of the present invention.

In the present application, terms such as “comprise” or “have” are intended to designate that a feature, number, step, operation, component, part, or combination thereof described in the specification exists, but one or more other features It is to be understood that it does not preclude the possibility of the presence or addition of numbers, steps, operations, components, parts, or combinations thereof. Also, terms such as first and second may be used to describe various elements, but the elements should not be limited by the terms. The above terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, a first component may be referred to as a second component, and similarly, a second component may also be referred to as a first component. The singular expression includes the plural expression unless the context clearly dictates otherwise.

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

Polyester foam sheet according to an embodiment of the present invention is a polyester resin foam sheet in which 90% or more of the cells are closed cells (DIN ISO4590).

In general, polyester resins have a lower melt viscosity than conventional foamed resins, so viscosity control is required by mixing additives to increase the viscosity. In this case, an anhydride such as pyromellitic anhydride is used as a crosslinking agent added for extrusion foaming of the polyester resin. In this case, as shown in Scheme 1 below, the OH group of the polyester molecule reacts with the COOH group of the anhydride, which is a crosslinking agent, thereby increasing the viscosity of the polyester and causing a thickening reaction in which the COOH group increases. However, when such a reaction proceeds a lot, crosslinking occurs as shown in Scheme 2 below, thereby causing a problem in that the sheet is brittle.

[Scheme 1]

[Scheme 2]

In order to solve this problem, in an embodiment of the present invention, the equivalent of the carboxyl end group (CEG, Carboxyl End Group) of the polyester resin forming the foam sheet is characterized in that less than 100 meq/g. Specifically, the equivalent of the carboxyl end group (CEG, Carboxyl End Group) of the polyester resin is 10 or more and less than 100 meq/g, 30 to 90 meq/g, 40 to 80 meq/g, 60 to 80 meq /g range or 60 to 90 meq/g range. By adjusting the equivalent of the carboxyl terminal group in the above range, the storage characteristics of the foam sheet can be improved. In particular, in the present invention, by controlling the equivalent of the carboxyl end group (CEG, Carboxyl End Group) of the polyester resin in the above range, the characteristics of the foam sheet excellent in thermoformability can be expressed.

When the equivalent of the carboxyl terminal group of the polyester resin forming the foam sheet is 100 meq/g or more, the foaming processability is poor, and the physical properties of the sheet are lowered, thereby causing the sheet to break.

In one embodiment, the foam sheet satisfies Equation 1 below.

[Formula 1]

y = 0.0471x + 56.417

In Equation 1, y is the equivalent of the carboxyl terminal group of the polyester resin forming the foam sheet, and x is the density of the foam sheet. At this time, in Equation 1, the unit is not considered, and only numerical values are calculated.

As such, the equivalent of the carboxyl terminal group of the polyester resin forming the foam sheet and the density of the foam seat are in a linear relationship, and as the density of the foam seat increases, the equivalent of the terminal carboxyl group tends to increase. .

On the other hand, the polyester resin may include an aromatic or aliphatic polyester resin synthesized from a dicarboxylic acid component, a glycol component, or hydroxycarboxylic acid. Non-limiting examples of the polyester resin include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polylactic acid (PLA), polyglycolic acid (PGA). ), polyethylene adipate (Polyehtyleneadipate, PEA), polyhydroxyalkanoate (Polyhydroxyalkanoate, PHA), polytrimethylene terephthalate (Polytrimethylene Terephthalate, PTT) and polyethylene naphthalate (Polyethylene naphthalate, PEN) may be more than Specifically, polyethylene terephthalate may be used as the polyester resin.

The average density according to KS M ISO 845:2012 of the manufactured foam sheet is 100 to 600 kg/m ³ , 100 to 500 kg/m ³ , 100 to 400 kg/m ³ , 100 to 300 kg/m ³ , 100 to 200 kg/m ³ , 200 to 600 kg/m ³ , 300 to 600 kg/m ³ , 400 to 600 kg/m ³ , or 500 to 600 kg/m ³ .

In addition, the average thickness of the foam sheet may be in the range of 1.0 to 10.0 mm. For example, the average thickness of the foam sheet is 1.0 to 5.0 mm, 1.0 to 4.0 mm, 1.0 to 3.5 mm, 1.0 to 3.0 mm, 1.0 to 5.5 mm, 1.0 to 2.0 mm, 1.0 to 1.5 mm, 1.5 to 5.0 mm , 2.0 to 5.0 mm, 3.0 to 5.0 mm, or 4.0 to 5.0 mm.

In one embodiment, the cell size of the foam sheet ranges on average from 100 to 700 μm. Specifically, the cell size of the foam sheet may be an average of 100 to 600 μm, 100 to 500 μm, 100 to 400 μm, or 350 to 500 μm, and more specifically, the cell size of the foam sheet is an average of 200 to 350 μm or 350 to 500 μm.

In one embodiment, the foam sheet according to the present invention includes calcium carbonate, which is an inorganic particle containing an alkaline earth metal carbonate in an appropriate range. The foam sheet can increase the surface uniformity and moldability of the sheet by uniformly mixing and foaming inorganic particles in the polyester resin.

Specifically, the foam sheet contains 0.5 to 5% by weight of inorganic particles. The content of the inorganic particles is in the range of 0.5 to 5% by weight, 1 to 5% by weight, 1.5 to 4.5% by weight, or 2 to 3.5% by weight. More specifically, the calcium carbonate may be added in an amount of 1.0 to 3.0 wt%, or 3.0 to 4.5 wt%.

In one embodiment, the alkaline earth metal element is at least one selected from the group consisting of calcium (Ca), magnesium (Mg) and barium (Ba). For example, the inorganic particles may be calcium carbonate (CaCO ₃ ), and the calcium carbonate may have an amorphous shape.

In a specific example, the average particle diameter of the inorganic particles is in the range of 1 to 5 μm. The average particle diameter of the inorganic particles may be, for example, 1.0 to 4.0 μm, 1.0 to 3.0 μm, 1.0 to 2.0 μm, 2.0 to 5.0 μm, or 3.0 to 5.0 μm.

The inorganic particles may have a thermal conductivity of 1.0 to 3.0 kcal/mh°C. Specifically, the thermal conductivity of the inorganic particles is 1.2 to 2.5 kcal / mh ℃, 1.5 to 2.2 kcal / mh ℃, 1.8 to 2.0 kcal / mh ℃, 1.5 to 2.5 kcal / mh ℃, or 1.8 to 2.3 kcal / mh ℃ days can As described above, the foam sheet including the inorganic particles has a uniform surface by exhibiting excellent thermal conductivity and can exhibit excellent thermoformability.

The polyester resin may have an intrinsic viscosity (IV) of 0.4 to 1.2 dl/g. Specifically, the intrinsic viscosity is 0.5 to 1.1 dl/g, 0.6 to 1.0 dl/g, 0.7 to 1.1 dl/g, 0.9 to 1.1 dl/g, 0.5 to 0.7 dl/g, 0.6 to 0.7 dl/g, 0.7 to 0.9 dl/g, 0.75 to 0.85 dl/g, 0.77 to 0.83 dl/g, or 0.6 to 0.8 dl/g.

A method of manufacturing a foam sheet according to an embodiment comprises the steps of: preparing a resin melt by mixing inorganic particles containing a polyester resin, a crosslinking agent and an alkaline earth metal carbonate; incorporating a blowing agent into the resin melt to form a foamable melt; and extruding and foaming the foamable melt to prepare a foam sheet.

Preparing the resin melt may be performed at a temperature of 260 ~ 300 ℃.

In addition, the resin melt contains 50 to 95% by weight of a polyester resin; 1-30 wt% of a crosslinking agent; and 1 to 30% by weight of inorganic particles.

The polyester resin may have the form of pellets, granules, beads, chips, and the like, and in some cases may be in the form of powder. In this case, the polyester resin is preferably in the form of a chip, and the equivalent of a carboxyl end group (CEG, Carboxyl End Group) of the polyester resin is preferably 50 meq/g or less.

The crosslinking agent corresponds to a thickener that improves the viscosity of the foamed resin, and a polyfunctional compound may be used. Such polyfunctional compounds include pyromellitic anhydride (PMDA), benzophenone dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 3,3',4,4'- Biphenyltetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl)ether dianhydride, bis(3,4-dicarboxyphenyl)thioether dianhydride, bisphenol A bisether dianhydride, 2,2-bis(3) , 4-dicarboxyphenyl) hexafluoropropane dianhydride, 2,3,6,7-naphthalene-tetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, 1,2,5,6 -naphthalene-tetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, hydroquinone bisether dianhydride, bis(3,4-dicarboxyphenyl)sulfoxide dianhydride and 3,4 It may be at least one selected from the group consisting of ,9,10-perylene tetracarboxylic dianhydride. Specifically, in the present invention, pyromellitic anhydride may be used as the polyfunctional compound.

Hereinafter, the present invention will be described in detail by way of Examples. However, the following examples are merely illustrative of the present invention, and the present invention is not limited by the following examples.

[Examples 1 to 4]

In order to prepare the polyester foam sheet, first, 100 parts by weight of polyethylene terephthalate (PET) resin was dried at 180° C. to remove moisture, and the PET resin was in the form of a chip, and the equivalent of the carboxyl terminal group was 50 meq/g or less. was used.

Based on 100 parts by weight of the PET resin from which moisture has been removed in the extruder, 5 parts by weight of pyromellitic dianhydride (PMDA), 0.1 parts by weight of a heat stabilizer (Iganox 1010) and 3 parts by weight of calcium carbonate having an average particle size of 1.0 to 5.0 μm are mixed and heated to 280° C. to prepare a resin melt.

Then, 1.5 parts by weight of butane as a foaming agent was added to the extruder based on 100 parts by weight of PET resin, and the resin melt was cooled to 250±2°C. The cooled resin melt was extruded while passing through a die, and a PET foam sheet having an average thickness of 2.0 mm was prepared. At this time, the density of the prepared PET foam sheet and the equivalent of CEG were adjusted as shown in Table 1 below.

[Comparative Example 1]

A foam sheet was prepared in the same manner as in Example 1, except that the density of the foam sheet and the equivalent of CEG were adjusted as shown in Table 1 below.

[Experimental example]

1) CEG equivalent

For the carboxyl end group (CEG, Carboxyl End Group) of the foam sheet, according to ASTM D 664 and D 4094, 0.2 g of the sample is placed in a 50 mL Erlenmeyer flask, 20 mL of benzyl alcohol is added, and a hot plate (hot plate) ) to 180°C and maintained for 5 minutes to completely dissolve the sample, then cooled to 160°C and when 135°C was reached, 5-6 drops of phenolphthalene were added, titrated with 0.02N KOH, and the color was changed from colorless to pink. CEG equivalent (COOH milli equiv./g sample) was calculated by Equation 1 below at the changing titration point. At this time, the calculated CEG equivalent is shown in Table 1 after rounding off.

[Formula 1]

CEG = (A-B)×20×1/W

In Equation 1, A is the amount of KOH consumed in titration of the sample (mL), B is the amount of KOH consumed in titration of the blank sample (mL), and W is the weight (g) of the sample.

2) Measurement of average thickness and expansion ratio of foam sheet (density measurement)

In order to measure the average thickness of each foam sheet, the overall width of each foam sheet was divided into 8 at regular intervals and the thickness was measured using an indicator (ID-C112, Mitutoyo Corporation), and then the average value was calculated.

In addition, in order to measure the average foaming density of each foam sheet, after taking a sample of each foam sheet with a width of 2 cm × 2 cm, the foam density was measured with an underwater electron density meter (EW300SG, MIRAGE).

Properties	Example 1	Example 2	Example 3	Example 4	Comparative Example 1
CEG equivalent (meq/g)	66	70	78	81	110-117
Thickness (mm)	2	2	2	2	2
Density (kg/m 3 )	200	280	450	520	350
Foam Fairness	Good	Good	Good	Good	error
sheet properties	Good	Good	Good	Good	bad (broken)

As can be seen from Table 1, it can be seen that the polyester foam sheet according to the embodiment has a carboxyl end group equivalent of less than 100 meq/g, and as the CEG equivalent is controlled low, foaming processability and sheet properties are good It can be seen that the results show In addition, it can be confirmed that the equivalent of the carboxyl terminal group of the polyester resin forming the foam sheet and the density of the foam sheet are in a linear relationship, and as the density of the foam sheet increases, the equivalent of the carboxyl terminal group tends to increase as well. could

On the other hand, the polyester foam sheet according to Comparative Example 1 had a CEG equivalent of 100 meq/g or more, which was confirmed as a result of cross-linking due to a large amount of reaction between PET and a cross-linking agent during extrusion foaming. In addition, in this case, it was confirmed that the foaming sheet was broken due to poor foaming processability.

Although the above has been described with reference to the preferred embodiment of the present invention, those skilled in the art or those having ordinary knowledge in the technical field will not depart from the spirit and technical scope of the present invention described in the claims to be described later. It will be understood that various modifications and variations of the present invention can be made without departing from the scope of the present invention.

Accordingly, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification, but should be defined by the claims.

Polyester foam sheet according to the present invention, by controlling the equivalent of a carboxyl end group (CEG, Carboxyl End Group) low, has a low dimensional change rate under high temperature conditions and excellent thermoformability characteristics of the foam sheet.

Claims (7)

1. A polyester resin foam sheet in which 90% or more of cells are closed cells (DIN ISO4590),

   A polyester foam sheet having an equivalent of less than 100 meq/g of carboxyl end groups (CEG, Carboxyl End Group) of the polyester resin forming the foam sheet.
2. The method of claim 1,

   The average thickness is 1 to 10 mm, and the average foaming density according to KS M ISO 845:2012 is 100 to 600 kg/m ³ Polyester foam sheet.
3. The method of claim 1,

   Polyester foam sheet satisfying the following Equation 1:

   [Formula 1]

   y = 0.0471x + 56.417

   In Equation 1 above,

   y is the equivalent of the carboxyl terminal group of the polyester resin forming the foam sheet,

   x is the density of the foam sheet.
4. The method of claim 1,

   The cell size of the foam sheet is an average of 100 to 700 ㎛ polyester foam sheet.
5. The method of claim 1,

   The polyester is a polyester foam sheet of polyethylene terephthalate (PET).
6. The method of claim 1,

   The foam sheet includes inorganic particles containing alkaline earth metal carbonate,

   The content of the inorganic particles is a polyester foam sheet in the range of 0.5 to 5% by weight.
7. 7. The method of claim 6,

   The alkaline earth metal element is at least one selected from the group consisting of calcium (Ca), magnesium (Mg) and barium (Ba),

   The average particle diameter of the inorganic particles is 1 to 5 ㎛ polyester foam sheet.