JPH08302170A - Reclaimed polyester resin composition and manufacture of thermoforming sheet - Google Patents

Abstract

PURPOSE: To reuse used thermoplastic polyester resin moldings such as used PET bottles as a sheet. CONSTITUTION: 100 pts.wt. resin grind obtained by grinding molded items of thermoplastic polyester resins is mixed with 10 to 50 pts.wt. polyethylene resin having a melt flow rate of 0.1 or below (g/10min measured according to JISK6760) and 1 to 10 pts.wt. compatibilizer. In addition, 10 to 50 pts.wt. amorphous thermoplastic polyester resin may be added thereto. The resulting product is excellent in extrudability into sheets and boards and can provide a sheet with high strengths. The additional use of an amorphous thermoplastic polyester resin can give a sheet excellent in also thermoformability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for reusing a used thermoplastic polyester resin molded product such as a PET bottle, and more particularly to a technique for reusing it as a thermoforming sheet.

[0002]

2. Description of the Related Art At present, PET (polyethylene terephthalate) bottles are mating to the needs of consumers and are in close contact with consumers' lives, and their production volume is enormous. Processing is a problem.
Generally, incineration or landfill disposal has been used as a treatment method for used plastic molded products, but it is difficult to say that these resources are effectively reused. Recycling for reuse is becoming socially important.

As a method of reusing a PET bottle that has become unnecessary, there is a method of crushing and melt-extruding it as a thread, and using it as a stuffed cotton or a carpet, but the amount is small,
As a method of reusing a vast number of PET bottles, it is desired to use the PET bottles with a higher throughput.

As one of the fields in which a large amount is used, it is considered that the material is melt-extruded into a thick sheet and used for various purposes. However, polyethylene terephthalate (which may be abbreviated as PET hereinafter), which is a raw material for PET bottles, has a very low viscosity in a molten state and a weak melt tension, and when it is a recycled product, it has a lower viscosity due to hydrolysis. Therefore, when melt extruding, the viscosity at the die outlet is very low, and it is extremely difficult to extrude a thick sheet into a sheet by a simple extrusion method. PE
The reason why T bottles are generally regenerated from carpet is that lower melt viscosity is better for the spinning process.

Large-sized applications of thick sheets include thermoforming applications such as vacuum forming and pressure forming, but PET is crystalline, and thick sheets are crystallized when the cooling rate is slow. It becomes a sheet and thermoforming becomes difficult. That is, in order to vacuum-form or pressure-form the crystallized sheet,
It does not soften unless it is preheated above the melting point of the crystal, which is about 260 ° C. Further, at such temperature, the melt tension is very low, the sagging is large, and the molding is very difficult. It becomes unrealistic from the viewpoint of time.

Even if a thick sheet having a low degree of crystallinity is obtained, since the crystallization start temperature during heating is close to the temperature at which vacuum forming or pressure forming is possible, the sheet is crystallized during preheating of forming. At first, it became hard and impossible to mold, or the temperature range at the time of molding was extremely limited, so the yield of product collection decreased and it was not suitable for actual production.

[0007]

In order to solve the above-mentioned problems, the present invention makes it possible to manufacture a thicker sheet by using a crushed material such as a PET bottle, and further, a thick material sheet that can be vacuum or pressure formed. And a melt flow rate (J) is added to 100 parts by weight of a resin crushed product obtained by crushing a molded product made of a thermoplastic polyester resin.
ISK6760, g / 10 min) is 10 to 50 parts by weight of a polyethylene resin of 0.1 or less and 1 to 10 parts of a compatibilizer.
The recycled polyester resin composition is obtained by mixing parts by weight.

Further, in order to obtain a thick sheet having good thermoformability, 100 parts by weight of a resin pulverized product obtained by pulverizing a molded product made of a thermoplastic polyester resin has a melt flow rate (JISK6760, g / 10 min) of 0. 1 to 10 parts by weight of polyethylene resin, 1 to 10 parts of compatibilizer
Parts by weight, and 10 parts of amorphous thermoplastic polyester resin
The gist is a regenerated polyester resin composition obtained by mixing 50 parts by weight to 50 parts by weight.

Furthermore, 10 to 50 parts by weight of a polyethylene resin having a melt flow rate (JISK 6760, g / 10 minutes) of 0.1 or less is added to 100 parts by weight of a resin crushed product obtained by crushing a molded product made of a thermoplastic polyester resin. Melt-extruding a recycled polyester resin composition obtained by mixing 1 to 10 parts by weight of a compatibilizing agent and 10 to 50 parts by weight of an amorphous thermoplastic polyester resin into a sheet, and cooling while nipped by a roll. The present invention provides a method for producing a thermoforming sheet.

The present invention will be described in detail below. A PET bottle is representative of a used molded article made of a thermoplastic polyester resin which is a subject of the present invention, but is not limited thereto. Also, PET bottles and PET
Of course, burrs, ears, defective products, etc. generated in the film manufacturing process can also be targeted. Here, PET is an ethylene terephthalate homopolymer used in the case of a bottle and may contain a small amount of a copolymerization component depending on the case, but in any case, it is crystalline.

A molded product made of this thermoplastic polyester resin is recovered after use and crushed or crushed to obtain a crushed product of the thermoplastic polyester resin, which can be selected from various known means, and is particularly limited. Not done.

As described above, this pulverized resin product has a very low viscosity in the molten state and a very low melt tension, and it is difficult to extrude it into a thicker sheet by itself, so by mixing it with a specific polyethylene resin. Improves extrudability.

The polyethylene resin referred to in the present invention is a commercially available polyethylene resin having a repeating structure derived from ethylene, which has a side chain even if its molecular structure is linear. It is also possible to use those having a crosslinked structure partially. Further, a copolymer resin containing a small amount of a copolymer component may be used, but a homopolymer is sufficient for the purpose of increasing the melt viscosity and melt tension in the present invention.

This polyethylene resin has a melt flow rate (JISK 6760, 190 ° C., 2.16 kg load, g / 10 minutes) of 0.1 or less, and its addition amount is 100 parts by weight of PET pulverized product. The range is 10 parts by weight or more and 50 parts by weight or less.

If the melt flow rate of the polyethylene resin exceeds 0.1 or if the addition amount is less than 10 parts by weight, the melt tension at the mouth of the die is low and drooping becomes large, and for example, for general-purpose ABS sheets. The vertical polishing roll, which is a manufacturing facility, causes inconvenience such as the fact that sheeting becomes impossible. The addition amount is 5
If the amount exceeds 0 parts by weight, it is not preferable because the original purpose of recycling PET bottles and the like is deviated.

The lower limit of the melt flow rate is such that it has fluidity such that it can be mixed with a PET pulverized product and extruded by a usual melt extruder, but the molecular weight is 500,000.
The so-called ultra-high molecular weight polyethylene exceeding the above range has a melting temperature range planned for the composition of the present invention (approximately 250 to 2).
Since it does not flow at 80 ° C., it is not suitable for the present invention. As long as it is a polyethylene resin having such a melt flow rate, any of so-called low density polyethylene, medium density polyethylene and high density polyethylene can be used,
High-density polyethylene is easily available commercially.

By the way, as it is, it is a combination of PET pulverized resin and polyethylene resin, which are poorly compatible materials, and the extrusion stability is poor, and the physical properties of the obtained sheet are also poor. Therefore, a compatibilizer must be added. I have to.

As the compatibilizing agent used in the present invention, various modified polyethylene known per se, that is, a polyethylene resin having a polar structure introduced in the main chain or side chain in the molecule can be used. For example, there may be mentioned acid-modified polyethylene obtained by grafting α, β-unsaturated carboxylic acid or its acid anhydride onto polyethylene. Examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, ethacrylic acid, maleic acid, fumaric acid and itaconic acid, and the amount thereof is generally about 0.1 to 10% by weight.
In addition, carboxylic acid esters such as those obtained by graft-polymerizing or random-copolymerizing alkyl acrylates, alkyl methacrylates and the like can also be used.

Further preferred compatibilizers are α and β
A resin obtained by copolymerizing glycidyl ester or glycidyl ether of unsaturated carboxylic acid in the main chain or side chain of polyethylene can be mentioned. Examples of the glycidyl ester or glycidyl ether of α, β-unsaturated carboxylic acid include glycidyl acrylate, glycidyl methacrylate, glycidyl ethacrylate, glycidyl itaconate, glycidyl malate, allyl glycidyl ether, 2-methylallyl glycidyl ether, and styrene-p. -Glycidyl ether, vinyl glycidyl ether, etc., and methyl acrylate, methyl methacrylate, vinyl acetate, etc. can be copolymerized with this as a third component. The amount of copolymerization component is generally from 1 to
It is 30% by weight, preferably 5 to 20% by weight.

Here, polyethylene modified with a carboxylic acid or an acid anhydride thereof is somewhat inferior in thermal stability and the decomposition of PET may be promoted by an acid, so modified with a carboxylic acid ester or a glycidyl ester / ether. Polyethylene is particularly preferred. These are generally excellent in thermal stability and have the advantage that they do not accelerate the decomposition of the PET crushed product during melting.

When the amount of the compatibilizing agent is less than 1 part by weight, the compatibilizing effect is insufficient, and when it exceeds 10 parts by weight, the effect does not increase any more. Therefore, the range of 1 to 10 parts by weight is preferable.

It is well known that when PET is blended with a modified polyolefin in which a polar structure is introduced into the molecule, the impact strength with notches is dramatically improved, and it is mainly applied in the injection molding field. In general, none of these modified polyolefins commercially available have such a high viscosity that the melt viscosity of PET can be dramatically improved in the temperature range planned in the present invention, and the present invention can be achieved by using them alone. However, it is necessary to use the polyethylene resin in combination.

Such a composition exhibits good extrusion moldability and can be melt extruded into a thick sheet, and the obtained sheet has good strength. It is also possible to heat-treat after forming the sheet to make the crystallinity high and uniform. However, since this sheet is a combination of PET and a crystalline resin such as polyethylene resin, if it is made a thick sheet, crystallization will proceed and it is not suitable for thermoforming applications such as vacuum forming and pressure forming.

Therefore, when a sheet for thermoforming is desired, it is preferable to further mix 10 parts by weight or more and 50 parts by weight or less of the amorphous thermoplastic polyester resin with 100 parts by weight of the PET pulverized product. The addition of the amorphous polyester resin lowers the crystallinity of the sheet and widens the temperature range in which vacuum molding and pressure molding can be performed.

The amorphous polyester referred to in the present invention may be any one that can be mixed with a crystalline polyester to reduce its crystallinity, and various amorphous copolyesters can be used. For example, ethylene terephthalate repeating units are mainly used, and 20 mol% or more of isophthalic acid, adipic acid, neopentyl acid or the like is copolymerized as an acid component, or diethylene glycol, polyalkylene glycol, neopentyl glycol, 1,4 as a diol component.
Examples include those obtained by copolymerizing 20 mol% or more of cyclohexanedimethanol and the like.

Particularly, terephthalic acid as an acid component, a copolymer obtained by using ethylene glycol and 1,4-cyclohexane dimethanol as a diol component, terephthalic acid and isophthalic acid as an acid component, and ethylene glycol as a diol component. It is practical to use one of these. As a measure of amorphousness, a differential scanning calorimeter (DSC) may be used to select a resin having a heat of crystallization (ΔH) of 5 cal / g or less when the temperature is lowered from the molten state at a rate of 10 ° C./min. .

When the mixing ratio of the amorphous polyester is less than 10 parts by weight, the crystallinity of the composition is still high as a sheet for vacuum forming and pressure forming, and as described above, the crystal during preheating of the forming is formed. When the mixing ratio exceeds 50 parts by weight, there are disadvantages such as deviating from the purpose of regenerating the crystalline polyester in addition to the cost up.

The preferable composition ratio of this composition is 100 parts by weight of PET pulverized product in consideration of extrusion moldability, sheet strength, thermoformability of the sheet and the like, and the purpose and cost of regenerating the crystalline polyester. It is in the range of 10 to 30 parts by weight of polyethylene resin / 1 to 5 parts by weight of compatibilizer / 10 to 30 parts by weight of amorphous polyester.

Further, as a part or all of the above-mentioned polyethylene resin and / or amorphous polyester, a recycled material can be used as long as it satisfies the above-mentioned characteristics.

In addition to the above components, stabilizers, antistatic agents, colorants and the like may be added to the composition of the present invention as appropriate, and a small amount of new PET raw material may be mixed.

An example of a method for forming a sheet from the composition of the present invention will be described with reference to FIG. 1. The above components are mixed with a blender to obtain a powder or flake mixture. Alternatively, the mixture may be pelletized in advance by an extruder, a kneader or the like.

Then, the sheet is put into an extruder 1 such as a single-screw extruder or a twin-screw extruder, extruded into a sheet shape from a T die 2 in a substantially horizontal direction, and while nipping the sheet through a vertical type three-roll polishing device 3. Set to a specified thickness and cool. The extrusion conditions may be adjusted according to the mixing amount of the polyethylene resin based on the usual PET extrusion conditions, and the cooling conditions by the polishing device are, for example, 40 to 10.
The sheet can be rapidly cooled by setting it to about 0 ° C. In order to produce a thick sheet as the object of the present invention,
In the method of casting a molten resin on a cooling drum which is applied to the production of a thin film, "warping" is likely to occur and it is difficult to obtain a flat sheet. Therefore, a method of cooling while nipping with a roll is suitable.

Although the sheet thickness varies depending on the application, the present invention is generally suitable for a sheet having a thickness range of about 0.5 to 5 mm, and includes a sheet generally called a plate. Of these, a thickness of about 0.5 to 3 mm is suitable as a thermoforming sheet. The present invention is particularly effective in the case of a sheet having a thickness of 1 mm or more, which has been extremely difficult to manufacture in the past. The sheet according to the present invention maintains the characteristics of PET such as strength, heat resistance, and rigidity, and the polyethylene resin has improved the weak points of PET, such as alkali resistance. Therefore, when used together with concrete which is a strong alkaline as a construction civil engineering material, it exhibits excellent resistance and also has good releasability from concrete. Also, the releasability from the mold in the case of thermoforming is improved.

When a sheet made of a composition containing an amorphous polyester is thermoformed, the conditions are different depending on the sheet thickness, but the sheet surface temperature is generally 120 ° C. to 160 ° C. It can be molded or pressure molded. It is preferable to heat the sheet for as short a time as possible so that crystallization of the sheet does not become remarkable.

[0035]

The present invention will be described below with reference to examples. Table 1
The composition shown in FIG. 2 was melt extruded so that the resin temperature at the outlet of the die was about 270 ° C., and passed through a vertical three-roll polishing device as shown in FIG. 1 to obtain a sheet having a thickness of 0.5 to 2 mm. . The roll temperature at this time is 50 ° C / from below.
It was set to 60 ° C / 70 ° C. The properties of the obtained sheet and the results of the vacuum forming test are shown in Table 1. Details of each material in the composition of Table 1 are as follows.

PET: Pulverized product of PET bottle PE1: High-density polyethylene, melt flow rate 0.02 PE2: High-density polyethylene, melt flow rate 0.2 Compatibilizer 1: Ethylene-glycidyl methacrylate-vinyl acetate copolymer resin ( Weight ratio 83/12/5) Compatibilizer 2: Ethylene-methyl methacrylate copolymer resin (weight ratio 80/20) Copolyester 1: Terephthalic acid / ethylene glycol (65 mol%) + 1,4-cyclohexanedimethanol (35 Amorphous copolymer resin copolyester 2: terephthalic acid (78 mol%) + isophthalic acid (22 mol) / ethylene glycol amorphous copolymer resin The sheet characteristics and the criteria for the vacuum forming test are As follows:

Extrusion processability ⊚: Small sagging at the outlet of the die allows sheeting without problems even with a thick sheet of 1 mm or more. O: Sheeting is possible up to a thickness of about 1 mm. X: Sagging is large and the polishing roll cannot be guided.

Strength ⊚: Even if the sheet is bent at room temperature, the whitening of the folded portion of the sheet is small, and it does not break even when repeatedly bent. ○: The bent portion is whitened but does not crack. X: When bent, cracks and delamination occur.

Vacuum Formability ⊚: Crystallization during preheating is slow, and a thick sheet of 1 mm or more can be formed. Good: Molding is possible up to a thickness of about 1 mm. ×: Crystallization occurs during preheating and solidifies to make molding impossible.

[0040]

[Table 1]

As is clear from the results shown in Table 1, the composition of the present invention had good extrusion moldability into a plate and good strength. However, Example 1 containing no amorphous polyester resin
Sheet was inferior in vacuum formability. It can be seen that the compositions of the respective sheets shown in Comparative Examples are outside the scope of the present invention, and problems such as difficulty in extrusion molding into a plate, insufficient strength, and difficulty in vacuum forming occur.

[0042]

INDUSTRIAL APPLICABILITY As described above, the regenerated polyester resin composition of the present invention is excellent in moldability into a sheet / plate, and a sheet having high strength can be obtained. Further, when an amorphous thermoplastic polyester resin is used together, a sheet excellent in thermoformability can be obtained. Therefore, the recycled polyester resin composition of the present invention is a flat plate, or various molded products obtained by thermoforming from the flat plate, for example, a temporary frame member for civil engineering or a cover for various devices.
It is effectively used as a material for housings, housing members, etc.
It helps to solve the problem of dust such as ET bottles.

[Brief description of drawings]

FIG. 1 is a side view illustrating a sheet manufacturing method of the present invention.

[Explanation of symbols]

 1 Extruder 2 T die 3 Polishing device

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Claims (3)

[Claims] 1. 100 parts by weight of a crushed resin product obtained by crushing a molded product made of a thermoplastic polyester resin, 10 to 50 parts by weight of a polyethylene resin having a melt flow rate (JISK 6760, g / 10 min) of 0.1 or less, and A recycled polyester resin composition obtained by mixing 1 to 10 parts by weight of a compatibilizer. 2. 10 to 50 parts by weight of a polyethylene resin having a melt flow rate (JISK 6760, g / 10 min) of 0.1 or less is added to 100 parts by weight of a resin crushed product obtained by crushing a molded article made of a thermoplastic polyester resin, 1 compatibilizer
10 parts by weight, and 10 to 50 parts by weight of the amorphous thermoplastic polyester resin are mixed to produce a regenerated polyester resin composition. 3. 10 to 50 parts by weight of a polyethylene resin having a melt flow rate (JISK 6760, g / 10 minutes) of 0.1 or less is added to 100 parts by weight of a resin crushed product obtained by crushing a molded article made of a thermoplastic polyester resin, 1 compatibilizer
10 to 10 parts by weight, and 10 to 50 parts by weight of an amorphous thermoplastic polyester resin are mixed to form a recycled polyester resin composition, which is melt-extruded into a sheet and cooled while being nipped by a roll. Sheet manufacturing method.