JPH0818414B2 - Moldable composite sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to a molding composite sheet comprising a nonwoven fabric and a resin sheet. More specifically, the present invention relates to a composite sheet excellent in thermoformability in which a long-fiber nonwoven fabric made of a semi-stretched polyester polymer is bonded to at least one surface of a polyester polymer low crystalline resin sheet.

Such a composite sheet has decorative properties, heat resistance, heat insulation, anti-condensation properties, etc., and is used for molding food trays (for example, trays that require heat resistance such as openable trays), automobiles, interiors, building materials, etc. It is used as an interior part.

[Conventional technology]

Conventionally, a large amount of polyethylene, polystyrene, etc. sheets have been used as molding materials in the food tray field.
In some cases, it was difficult to use these materials because of their heat resistance. In the field of dual openable food trays (which can be cooked in a microwave oven and oven), polyester-based molded products have been rapidly spreading in recent years, mainly in the United States.

The molding material used in this field is called crystallized polyester (hereinafter referred to as C-PET), which is a low crystalline polyester added with a crystal nucleating agent so that crystallization progresses in the molding process and heat resistance is imparted. It is a resin sheet that deforms at a relatively low temperature and can be vacuum molded, pressure molded, or full-press molded. Therefore, crystallization proceeds at the same time as molding, and a molded product excellent in heat resistance and shape retention can be obtained. Molding C-PET resin or sheet is commercially available for heat-resistant food containers.

However, one of the problems with the C-PET resin sheet is that, unlike general sheet molding, the progress of crystallization in the resin sheet changes depending on the heat history from the preheating step to the molding step, and thus it is obtained. Since the heat resistance and strength of the molded product change, accurate temperature control is necessary. For example, if the preheating step is omitted or full-press molding is performed under insufficient conditions, a rapid flow occurs at 100 ° C to 150 ° C, which causes problems such as breakage of the molded product and perforation.

In addition, the dual openable tray means that frozen food is reheated in the microwave or oven.
Although it is used in a very wide temperature range of ℃ to 220 ℃, another problem with the current C-PET resin sheet molded product is that it has low cold impact strength.

This is because crystallization in the molding process progresses and many spherulites are formed during molding, and the heat resistance of the molded product is improved, but it becomes a hard and brittle structure.To solve this problem, the resin sheet It has been attempted to increase the thickness of the resin or to increase the molecular weight of the polyester resin, but this is not always practical because the manufacturing cost of the polymer also increases.

[Problems to be solved by the invention]

The object of the present invention is to make use of the excellent properties of the C-PET resin sheet for molding, and to make the optimum molding temperature range narrow due to tearing of the sheet during thermoforming and uneven thickness. And the drawback of low cold shock resistance when using the molded product, and the molded sheet product with functions such as decorativeness, heat resistance and dew condensation prevention added to the molded product. Is to provide.

[Means for solving problems]

The object of the present invention is achieved by a composite sheet characterized in that a long-fiber nonwoven fabric using semi-stretched fibers of a polyester polymer is bonded to at least one surface of a resin sheet of a polyester polymer having a low crystallinity.

The nonwoven fabric used in the composite sheet according to the present invention, by a known spunbond method, a polyester-based polymer, obtained by melt spinning at a spinning speed of 2000 to 4000 m / min, birefringence 0.02 ~ 0.07, density 1,330 ~. 1,3
A long-fiber web made of 60 semi-stretched polyester fibers was heated at 70 ℃ to 10 ℃ using a pair of hot rolls with embossed patterns.
It is advisable to use a nonwoven fabric obtained by embossing at a pressure-bonding area ratio of 3 to 50% at 0 ° C., or a nonwoven fabric obtained by further embossing with a high temperature (120 ° C. to 200 ° C.) embossing roll.

In particular, the latter is a non-woven fabric proposed by the same applicant as the present invention in Japanese Patent Application No. 60-203418, in which boiling water shrinkage is within 10%, breaking elongation at 150 ° C is 70% or more, and at 150 ° C. Has a characteristic of 30% elongation stress of 50 kg / cm ² or less, and can be thermoformed in a wide temperature range of 120 to 220 ° C without causing fusion to all molds, film formation, and tearing during thermoforming. . A non-woven fabric with excellent moldability.

The non-woven fabric used in the present invention may be a mixture of other fibers within a range not impairing the object of the present invention, for example, synthetic fibers such as polyolefin and polyamide, or natural fibers such as rayon. I can. The fineness of the fiber is 30 denier or less, preferably 0.5 to 10 denier. on the other hand,
The basis weight of the non-woven fabric is preferably 10 to 500 g / m ² .

The moldable composite sheet of the present invention can be obtained by joining and integrating the above-mentioned semi-stretched polyester continuous fiber non-woven fabric and the low crystalline polyester resin sheet.

The moldable composite sheet of the present invention solves the problems of the C-PET resin sheet, and by being combined with the above-mentioned long-fiber nonwoven fabric, the molding process can be favorably performed in a wide temperature range,
The cold shock resistance of the molded product can be greatly improved.
That is, since the non-woven fabric in the composite sheet is bulky, it has cushioning properties, and even at low temperatures, since it is a non-woven fabric made of semi-stretched yarn, it has a high impact strength.

As the polyester resin sheet used in the present invention,
A polyester-based polymer (especially polyethylene terephthalate is heat-resistant to which a crystal nucleating agent such as calcium carbonate or magnesium carbonate has been added in advance, so that crystallization progresses during heat-molding and the heat resistance of the obtained molded product is imparted. , Which is preferable from the viewpoint of strength) is a resin sheet having a crystallinity index of 10% or less, which is produced by rapidly cooling a sheet made by extruding using a T-die and a flex slip die, and is generally used for heat-resistant food trays. Commercially available products can be used. or,
As the resin sheet, a resin sheet having a multi-layered structure with films of polyvinylidene chloride, polyamide or the like can be used depending on the purpose such as barrier property.

The non-woven fabric in the moldable composite sheet of the present invention, and C-PE
The T resin sheet is joined by a method of joining using an embossing roll heated to a temperature of 70 ° C to 100 ° C, or by applying an adhesive to the resin sheet and the nonwoven fabric with a gravure roll, a kiss roll, a spray, or the like. It can be selected according to the purpose such as the method of joining.

The thus obtained composite sheet for molding of the present invention can be molded into a deep concave-convex shape or a complicated shape by vacuum molding, pressure molding, press molding with a concave-convex mold, and the like.

The molded product obtained by the molding is a composite of long-fiber non-woven fabric made of fiber material, so it has excellent cold impact strength, tear strength, etc., and has excellent functions such as decorativeness, heat insulation, and dew condensation prevention. have. Therefore, it can be widely used as a molding material such as a packaging material, an automobile interior material, and a building material as well as the above-mentioned food tray.

〔Example〕

Hereinafter, the present invention will be specifically described with reference to examples. The definitions of physical properties and measuring methods described in Examples and others are shown below.

◎ Density The density was measured using a calcium nitrate-water density gradient tube. The sample is preliminarily immersed in a low-density liquid for 1 hour under reduced pressure to defoam, then placed in a density gradient tube and allowed to stand at 30 ° C. for 20 hours, and the density is determined from the density of the liquid in which the sample is located.

◎ Boiled water shrinkage rate A sample of 25 cm × 25 cm was placed on each of the vertical and horizontal positions at 20 cm, immersed in boiling water for 5 minutes, taken out, and the dimensional change of the sample was measured. The shrinkage rate is shown as an average value of N = 5.

Birefringence index Under white light, the birefringence index (Δn) is measured using a polarizing microscope Bereck compensator.

◎ Strength and Elongation: (according to JIS-L-1096) Grasping by Shimadzu's Auto Graph DSS-2000 type universal tensile tester 10cm long, tensile speed 20cm / min measured at 25 ℃ and 150 ℃ Ask.

The 30% elongation stress is represented by the value obtained by dividing the strength at 30% elongation by the cross-sectional area of the sample.

◎ Abrasion resistance A 20 cm vertical × 3 cm horizontal test piece was rubbed 100 times with a friction tester type II (Gakushin type) at a load of 500 g, and then the appearance change of the test piece was judged according to the following criteria. As a guideline for abrasion resistance.

(Judgment criteria) Class A: No fuzz at all.

Class B: Some fluff but not noticeable.

Class C: Conspicuous fuzz.

◎ Breathability: (JIS-L-1096 method) Measured using a Frajour tester.

◎ Thermal deterioration After leaving in a 105 ° C hot air dryer for 300 hours, perform a tensile test and measure the breaking elongation. The elongation retention is calculated from the elongation at break before and after exposure at 105 ° C.

L ₁ : elongation at break before exposure, L ₂ : elongation at break before exposure, ◎ Tear strength: (according to JIS-L-1096) A test piece of 5 cm x 15 cm is taken in each of the vertical and horizontal directions, and the tensile tester is used. (Single tongue method).

◎ Crystallinity index The crystallinity index of X-ray diffraction intensity in the equatorial direction is determined by the equatorial reflection method.

The X-ray diffraction intensity is the X-ray generator (RU-200P manufactured by Rigaku Denki Co., Ltd.).
L) and a goniometer (SG-9R), a scintillation counter for the measuring tube, a wave height analyzer for the counting unit, and a Cu / Kα ray (wavelength = 1.54) monochromated with a nickel filter.
18A). The sample is set in an aluminum sample holder so that the axis of the sample is perpendicular to the X-ray diffraction plane. At this time, the thickness of the sample is set so as to be about 0.5 m / m. Operating X-ray generation at 30KV, 80mA, scanning speed 1 ° / min, chart speed 10mm / min, time constant 1 second, divergence slit 1/2 °, receiving slit 0.3m / m, scattering slit 1 /
Record the diffraction rate at 2 ° from 2 ° 35 ° to 7 °. The full scale of the recorder is set so that the diffraction intensity curve is within the scale. Polyethylene terephthalate resin sheet generally has an equatorial line diffraction angle 2θ = 17 ° to 26 °
Has three major reflections in the range of [low angle side (100)
(010) (110) plane]. FIG. 1 shows an example of the X-ray diffraction intensity curve of the polyethylene terephthalate resin sheet. (In the figure, a represents a crystal part and b represents an amorphous part.) The crystallinity index is 2 from the obtained X-ray diffraction intensity curve.
A straight line connects the diffraction intensity curves between θ = 7 ° and 2θ = 35 ° to form a baseline. As shown in Fig. 1, 2θ = 20 °
Along the low-angle side and the high-angle side of the valley with the neighboring valleys as vertices, a straight line is connected to separate the crystalline part and the amorphous part, and the area is calculated according to the following formula.

◎ Cold shock resistance A 30 mmφ hole in the center and an 8R edging in the hole Vertical 10 cm × width 10 cm × height 3 cm made of iron, 10 cm square sample on the sample mounting table Is fixed and placed in a container with an ambient temperature of 0 ° C. and −20 ° C., a metal ball with a load of 150 g is dropped, and the height is expressed so that the sample does not break.

Example 1 Using a rectangular spinneret having a hole diameter of 0.25 mm and 1000 holes, polyethylene terephthalate having an intrinsic viscosity of 0.75 was spun at a melting temperature of 290 ° C. at a discharge rate of 850 g / min, and the position was 1000 mm directly below the spinneret. A long fiber web having a basis weight of 100 g / m ² was taken out on the wire mesh conveyor at spinning speeds of 2500 m / min, 3000 m / min and 3500 m / min while changing the air pressure of the index air sucker. Table 1 shows the fiber characteristics of the obtained web.

As a comparative example, long fiber webs having spinning speeds of 1300 m / min and 5000 m / min were sampled and shown in Table 1 as an example other than the present invention.
A web composed of each fiber having the characteristics shown in Table 1 was subjected to partial thermocompression bonding between an embossing roll having a convex portion having a unit area of 2 mm ² and a compression area ratio of 13% and a lower roll having a smooth surface. . The conditions for partial thermocompression bonding are 85 for the upper and lower rolls.
℃, linear pressure 20kg / cm. Next, partial thermocompression bonding was further performed using an embossing roll having a convex area having a unit area of 0.8 mmφ and a compression bonding area ratio of 5%. Partial thermocompression bonding conditions are an upper and lower roll temperature of 150 ° C and a linear pressure of 20 kg / cm. The properties of the resulting nonwoven fabric are shown in Table 2.

However, Comparative Example Experiment No. is a non-woven fabric partially thermocompressed at an upper and lower roll temperature of 235 ° C., because thermocompression bonding does not work at 85 ° C. and 150 ° C.

It can be said from Table 2 that the nonwoven fabric used in the present invention is
It has a low boiling water shrinkage, a high elongation at break of more than 70% at 150 ° C, and a 30% elongation stress of 50 kg / c during heating.
It was as low as m ² or less, and it was found that moldability of deep uneven shapes and complicated shapes could be easily performed.

On the other hand, Comparative Example Experiment No. is brittle, inferior in extensibility, heat deterioration, etc., and is not suitable as a molding material, and there are many problems in the process due to fusing and roll peeling during embossing. Met.

Further, Comparative Example Experiment No. was a non-woven sheet having a large 30% elongation stress at 150 ° C. and a small elongation and poor thermoformability.

Example 2 The nonwoven fabric of Example 1 (having the properties shown in Table 2) and 75 μ of a low crystalline polyester resin sheet (manufactured by Eastman, crystallinity index 6%) were joined. The joining was performed by applying a room temperature curing type urethane adhesive (Takeda Pharmaceutical Co., Ltd., 2 liquid reaction type) at about 15 g / m ² . The properties of the obtained composite sheet are shown in Table 3.

However, Comparative Example Experiment No. shows the low crystalline polyester resin sheet, and Comparative Example Experiment No. also shows the resin sheet obtained by heat-treating the low crystalline polyester resin sheet at 150 ° C. for 5 minutes.

It can be seen from Table 3 that the molding composite sheet of the present invention has a rupture elongation at 150 ° C. of more than 70% and has a 30% elongation stress of 50 kg / cm ² or less when heated. Since it is low and the thermal characteristics are almost the same as those of the non-woven fabric, it was found that it is possible to easily form a deep uneven shape and a complicated shape.

The composite sheet of the present invention has low air permeability, and can be vacuum-formed or pressure-formed.

Furthermore, the composite sheet of the present invention was excellent in tear strength and cold impact resistance.

On the other hand, it was found that the resin sheets of Comparative Example Experiment No. had extremely low tear strength and cold impact resistance, were brittle, and were easily broken.

Example 3 Example No. of composite sheet example obtained in Example 2
Using Comparative Example Experiment No., molding was performed. Molding process is a hemispherical mold with a diameter of 10 cm and a maximum radius of 10 cm at 180 ° C.
It was heated to and press-molded. As a result, the maximum radius
It could be easily molded up to 5 cm, and a molded product with a height of 4.9 cm was obtained.

Then, the molded product was heat-treated in a microwave oven at a temperature of 180 ° C. for 30 minutes. There was no dimensional change or deformation of the molded product before and after the heat treatment.

From the above, it was found that the moldable composite sheet of the present invention is excellent in moldability, shape retention of a molded product, and heat resistance.

On the other hand, the resin sheet of Comparative Example Experiment No. melted at the same time when it contacted the mold during the molding process. From this, it was found that it is necessary to set the temperature range of the molding process of the resin sheet to the optimum condition.

〔The invention's effect〕

Since the moldable composite sheet of the present invention is a composite sheet of a semi-stretched polyester long-fiber non-woven fabric having a small heat shrinkage and being easily stretched in a wide molding temperature range and a low crystalline polyester resin sheet, it is deep. It is possible to mold irregular shapes and complex shapes, and the molded product has excellent shape retention. It is widely used as a molding material for food trays, packaging materials, wall covering materials, automobile interior materials, etc., because it has excellent decorating properties, heat resistance, heat insulation properties, and dew condensation prevention properties of the deplasticized image.

[Brief description of drawings]

Figure 1 shows the X of polyethylene terephthalate resin sheet.
It is a graph which shows an example of a line diffraction intensity.

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location B29C 51/14 7619-4F

Claims (3)

[Claims] 1. A moldable composite sheet comprising a long-fiber non-woven fabric using semi-stretched fibers of a polyester-based polymer bonded to at least one surface of a low-crystalline resin sheet of a polyester-based polymer. 2. A polyester-based long-fiber nonwoven fabric having a boiling water shrinkage of 10% or less, a breaking elongation at 150 ° C. of 70% or more, and a breaking elongation of 30 at 150 ° C.
The moldable composite sheet according to claim 1, wherein the% elongation stress is 50 kg / cm ² or less. 3. The moldable composite sheet according to claim 1, wherein the resin sheet is a low crystallinity polyethylene terephthalate resin sheet containing a crystal nucleating agent and having a crystallinity index of 10% or less.