JP7178787B2 - LAMINATED SHEET AND MANUFACTURING METHOD THEREOF AND MOLDED PRODUCT - Google Patents

Description

TECHNICAL FIELD The present invention relates to a laminated sheet that does not use an adhesive and has excellent adhesiveness and transparency, a method for producing the same, and a molded article obtained from the laminated sheet.

Polyester resins typified by polyethylene terephthalate (hereinafter referred to as “PET”) have excellent chemical and physical properties. Polyester resins are widely used for containers such as beverage bottles, films, sheets, and the like. In order to exhibit various functions, a laminated sheet is used in which a polyester film is laminated on a polyester base sheet. In such a laminated sheet, it is necessary to bond the polyester-based base sheet and the polyester-based film.

In order to thermally bond polyester resins together, it is usually necessary to heat them to near the melting point. However, such heating makes it difficult to maintain the shape of the film and base sheet, so such bonding by heating is not practical. Therefore, in order to thermally bond polyester resins together, an adhesive that can be fused at least at a temperature lower than the melting point of the polyester resin is usually required. For example, Patent Document 1 aims to provide a resin film imparted with rigidity without degrading optical properties, and two or more stretched resin substrates are laminated together with an adhesive layer having a constant thickness. A resin film is disclosed.

On the other hand, Patent Document 2 describes a multilayer sheet that does not use any adhesive and has excellent transparency, adhesive strength, and reusability, and a method for producing the same. In this method, the resin sheets are brought into close contact with each other through water and then heated and pressurized to bond the resin sheets together.

JP 2012-161966 A Japanese Patent No. 5539805

In the laminated sheet obtained by laminating resin sheets with an adhesive, which is described in Patent Document 1 and the like, air bubbles are entrained in the adhesive layer when the substrates are laminated together, or air bubbles are generated due to the reaction of the adhesive. It is known that the adhesiveness and transparency of the adhesive layer are deteriorated by the heat (see paragraph [0013] of Patent Document 1).

On the other hand, it is known that even in a method of laminating resin sheets without using an adhesive, the adhesion and transparency of the adhesive layer are deteriorated due to air bubbles entering between the substrates (Patent Document 2, paragraph [0007]). In order to solve such a problem, it is not sufficient to simply bond resin sheets together without using an adhesive, and a special manufacturing method as described in Patent Document 2 is required.

An object of the present invention is to provide a laminated sheet that does not use an adhesive and has excellent adhesiveness and transparency, a method for producing the same, and a molded article obtained from the laminated sheet.

The polyester-based laminated sheet of the present invention is a sheet in which a polyester-based film is directly laminated on a polyester-based base sheet, and a test piece having a width of 15 mm is taken. It is characterized by having a peel strength (according to JIS Z 0238) with respect to the polyester film of 0.98 N or more and a total light transmittance of 85% or more.

The molded article of the present invention is characterized by being obtained by thermoforming the polyester-based laminated sheet of the present invention.

The method for producing a polyester-based laminated sheet of the present invention comprises a step of directly placing a polyester-based film on a polyester-based base sheet to obtain a laminate, and pressing the laminate twice at a roll temperature of 130°C to 150°C. or a step of bonding the polyester base sheet and the polyester film by pressure bonding at a roll temperature of 120° C. to 150° C. three times or more.

The polyester-based laminated sheet of the present invention can adhere a substrate and a sheet without using an adhesive, and is excellent in adhesiveness and transparency. Therefore, the polyester-based laminated sheet of the present invention can be suitably used for applications that require adhesiveness and transparency, such as packaging containers for food and drink. Moreover, according to the manufacturing method of the present invention, the laminated sheet of the present invention having the above advantages can be easily manufactured.

It is a figure which shows the outline of the drum laminator of an Example. FIG. 10 is a diagram showing another example of a drum laminator; It is a graph which shows the result of the peel strength of an Example. 4 is a graph showing the results of total light transmittance of laminated sheets of Examples. 4 is a graph showing haze value results of laminated sheets of Examples.

An embodiment of the present invention will be described below. This embodiment is an example of implementing the present invention, and the present invention is not limited to this embodiment.

(1) Polyester-Based Laminated Sheet In the polyester-based laminated sheet according to the present embodiment (hereinafter referred to as "this laminated sheet"), a polyester-based film is directly laminated on a polyester-based base sheet. That is, the laminated sheet has a base sheet layer and a film layer in which the polyester base sheet and the polyester film are bonded together without using an adhesive. As a result, deterioration in adhesiveness and transparency due to the use of the adhesive can be suppressed.

The polyester-based base sheet and the polyester-based film contain a polyester resin as a main component. The "main component" is 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, more preferably 80% by mass or more, and particularly preferably 90% by mass or more, of the total resin components. It means contained. Therefore, the polyester-based base sheet and the polyester-based film may be composed only of a polyester resin, or may contain other resins within a range that does not significantly impair the adhesiveness and transparency. Further, the polyester resin may be of one type, or two or more different polyester resins may be used.

The polyester resin is not limited to a specific structure or type as long as it is a polycondensate of polycarboxylic acid or its derivative (ester, anhydride, etc.) and polyalcohol. A dicarboxylic acid is usually used as the polycarboxylic acid, and a diol is usually used as the polyalcohol. As the polyvalent carboxylic acid, for example, an aromatic polyvalent carboxylic acid can be used. The polyester resin may be a polycondensate of the polyvalent carboxylic acid or derivative thereof and the polyalcohol, or may be a copolymer obtained by copolymerizing with another monomer such as a monomer having a vinyl group such as styrene. It may be a polymer. Also, the polyester resin may be a polyester resin modified with another resin (for example, an epoxy resin).

Specific examples of the polyester resin include polyethylene terephthalate (PET), polypropylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene-1,2-bis(phenoxy)ethane-4,4′- Dicarboxylates, and polycyclohexylene dimethylene terephthalate. PET is preferable as the polyester resin. The PET may be a copolymer of terephthalic acid as an acid component and a single diol component, or may be a copolymer of two or more diol components.

The polyester resin may be in either a crystalline state or an amorphous state. From the viewpoint of moldability, the polyester resin is preferably amorphous polyester resin, more preferably amorphous PET. In addition, the "amorphous state" includes a non-crystallized state and a completely non-crystallized state. For example, "amorphous PET" includes PET in an uncrystallized state such as A-PET and PET in a completely uncrystallized state such as PET-G. The polyester base sheet is preferably amorphous polyester resin, more preferably amorphous PET, and still more preferably A-PET. The polyester film is preferably amorphous polyester resin, more preferably amorphous PET.

The polyester resin may be unstretched or stretched. For example, biaxially stretched polyester can be used as the polyester resin. The draw ratio is not particularly limited, but a low draw ratio is preferable because the formability of the laminate sheet is improved. Specifically, the draw ratio can be in the range of 2 to 7 times, preferably 2 to 5 times. In the case of biaxial stretching, it is preferable to stretch in the above ranges in both the longitudinal and transverse directions. An unstretched polyester base sheet is preferable as the polyester base sheet. As the polyester film, a low draw ratio, specifically a polyester film with a draw ratio within the above range is preferred.

A specific combination of the polyester resins constituting the polyester base sheet and the polyester film is not particularly limited. Specific examples of this combination include a combination of unstretched polyester as the polyester base sheet and stretched polyester as the polyester film. At least one of the polyester base sheet and the polyester film is preferably amorphous polyester resin. More preferably, both are amorphous polyester resins.

In the laminated sheet, preferably, the polyester base sheet is an unstretched amorphous polyester resin, and the polyester film is a stretched amorphous polyester resin. Particularly preferably, the polyester base sheet is unstretched A-PET, and the polyester film is stretched amorphous PET.

The total light transmittance of this laminated sheet is 85% or more. Therefore, this laminated sheet is excellent in transparency. The total light transmittance is a value measured according to JIS K 7361.

In the laminate sheet, the peel strength between the polyester base sheet and the polyester film is 0.98 N or more, preferably 1.07 N or more, more preferably 1.17 N or more, and more preferably 1.27 N or more. . This peel strength is a value measured according to the method described in Examples, ie, a test piece having a width of 15 mm at a peel rate of 300 mm/min and a peel angle of 180° in accordance with JIS Z 0238.

There is no particular limitation on the specific range of the haze value of the laminated sheet. The haze value of the laminated sheet is usually 6.0% or less, preferably 5.5% or less, more preferably 5.0% or less. The haze value is a value measured according to JIS K7136. It is preferable that the haze value is within the above range because the transparency is excellent.

The thicknesses of the laminate sheet, the base sheet layer and the film layer can be appropriately determined according to need. The thickness of the base sheet layer is usually 100-1000 μm, preferably 150-700 μm, more preferably 200-500 μm. Also, the film layer may be the same as or thinner than the base sheet layer. The thickness of the film layer is usually 1-100 μm, preferably 5-50 μm, more preferably 7-25 μm.

The laminated sheet may be composed only of the base sheet layer and the film layer, or may have other layers as necessary.

There is no particular limitation on the method for obtaining the laminated sheet. The laminated sheet can be usually obtained by the production method of the present invention.

The base sheet layer and the film layer may contain other components, if necessary, as long as the adhesiveness and transparency are not significantly impaired. Specific examples of the other components include additives used in known resin sheets, such as flame retardants, ultraviolet absorbers, fluorescent whitening agents, antistatic agents, antifogging agents, lubricants, and antiblocking agents. agents, flow improvers, plasticizers, dispersants, and antimicrobial agents.

There are no particular limitations on the shape, dimensions, and specific uses of the laminated sheet. As will be described later, this laminated sheet can be used to obtain various molded articles by molding. Specific examples of the molded article include containers such as packaging containers, for example, food and drink packaging containers. Thus, the laminated sheet can preferably be used for thermoforming or manufacturing molded articles, more preferably for manufacturing packaging containers. In addition, the said "container" includes not only the whole container but a part of container. For example, the "container" includes not only the main body of the container but also the lid of the container.

(2) Molded article A molded article according to the present embodiment (hereinafter referred to as "this molded article") is obtained by thermoforming the present laminated sheet. The specific method of thermoforming is not particularly limited, and known thermoforming methods such as hot platen forming, vacuum forming, pressure forming, or vacuum pressure forming can be used. Also, the conditions for thermoforming are not particularly limited. Molding conditions can be appropriately determined as necessary.

There are no particular restrictions on the shape, dimensions, and specific uses of the molded article. Applications of the present molded product include containers such as packaging containers, for example, food and drink packaging containers. In addition, the said "container" includes not only the whole container but a part of container. For example, the "container" includes not only the main body of the container but also the lid of the container.

(3) Method for producing a polyester-based laminated sheet In the method for producing a polyester-based laminated sheet according to the present embodiment (hereinafter referred to as "this method"), a polyester-based film is directly placed on a polyester-based base sheet. A step of obtaining a laminate is included. The above description is valid for the polyester-based base sheet and the polyester-based film. In addition, in addition to the case where the polyester film is directly placed on the polyester base sheet, in addition to the case where the polyester film is directly placed on the polyester base sheet, and a case where the polyester base sheet is directly placed on the polyester film.

A specific method for obtaining the laminate is not particularly limited. The laminate may be formed at least at the initial stage of pressing the laminate with a pair of rolls. Usually, as shown in FIG. 1, the laminate is obtained by rolling a polyester base sheet and a polyester film supplied from a polyester base sheet roll and a polyester film roll to an appropriate roll (No in FIG. 1). .1 by placing the polyester film directly on the polyester base sheet through a roll on the upstream side of the roll 1).

In this method, the laminate is pressed twice at a roll temperature of 130° C. to 150° C. or pressed three times or more at a roll temperature of 120° C. to 150° C. to bond the polyester base sheet and the polyester film. including the step of allowing This step can improve the adhesiveness and transparency of the resulting laminated sheet.

"Two times crimping" and "three or more crimping" mean that crimping by a pair of rolls is performed twice or three times or more. For example, the drum laminator shown in FIG. 1 has three pairs of rolls (No. 1 to No. 3). Of these, No. 1 and No. 2 or No. If crimping is performed by No. 3 rolls, it becomes "twice crimping". 1 to No. If crimping is performed by 3 rolls, it becomes "three times crimping".

The specific configuration of the "pair of rolls" is not particularly limited as long as the laminate can be pressure-bonded between the rolls and the heating roll. The "pair of rolls" is, for example, a case where two or more sets of independent rolls and heating rolls are provided as shown in FIG. 2, or two or more independent rolls and a single roll as shown in FIG. heating drum combination.

The roll temperature means one of the pair of rolls, usually the roll that is in contact with the polyester film.

This method may optionally include other steps than the above steps as long as the adhesiveness and transparency of the resulting laminated sheet are not significantly impaired.

EXAMPLES The present invention will be specifically described below with reference to Examples. It should be noted that the present invention is not limited to the forms shown in the examples. The embodiments of the present invention can be variously modified within the scope of the present invention depending on the purpose, application, and the like.

(1) Production of Laminate Sheet A-PET (PET resin “CB-602” manufactured by Far Eastern New Century Co., Ltd., thickness 0.35 mm×width 500 mm) was used as a polyester base sheet. In addition, as a polyester film, a biaxially stretched shrink film that is a PET-G-like amorphous polyester (manufactured by Toyobo, grade name “SC821”, draw ratio: 3 times in length × 4 times in width, 12 μm in thickness × 490 mm in width) It was used.

A laminated sheet was produced by thermocompression bonding the base sheet and the film with a drum laminator. Details of the drum laminator are shown in FIG. The drum laminator has three pressure rolls (No. 1-3). In Table 1, the "number of crimping times" of 1 means crimping roll No. 1 only, and the "number of times of crimping" is 2 times, crimping roll No. 1 and no. 2 is used, and the "number of times of crimping" is 3 times. 1 to 3 are used to indicate thermocompression bonding. The line speed is 5 m/min.

(2) Peel strength From each laminated sheet obtained by the above method, strip-shaped test pieces with a width of 15 mm were cut out (n=3). About 20 mm of the edge of the film constituting the laminated sheet is peeled off, the edge of the film and the base sheet from which the film is peeled off are each held with a jig, and the film and sheet are rotated in a 180° direction at a speed of 300 mm/min according to JIS Z 0238. The film was pulled to measure the test force when the film was peeled off. The results are shown in Table 1 and FIG. In Table 1, "-" indicates that the measurement was not performed because it was in an unbonded state. In addition, "*" in Table 1 indicates that the film was torn during the measurement and the measurement was not possible.

From Table 1 and FIG. 3, when the roll temperature was 120° C. and the pressure bonding was performed once or twice, the base sheet and the film were not bonded, while the peel strength was 1.10 N when the pressure bonding was performed three times. . Also, at a roll temperature of 130° C. to 150° C., the peel strength was higher in two or three times pressure bonding than in the case of one time pressure bonding. In particular, at a roll temperature of 130 ° C to 140 ° C, compared to the case of one time crimping, in the case of two or three times crimping, it is 8 times or more (twice crimping) and 15 times or more (three times crimping) of one time crimping. It showed high peel strength. From these results, it can be seen that by pressing twice at a roll temperature of 130° C. to 150° C. or pressing three times or more at a roll temperature of 120° C. to 150° C., adhesion between the base sheet and the film can be achieved without using an adhesive. It can be seen that a laminated sheet having excellent properties can be obtained.

Moreover, since the shrink film used in this example shrinks when heated, it is likely to shrink or wrinkle during lamination. When the temperature of the heating roll is raised, the adhesion between the base sheet and the film is strengthened, but shrinkage tends to occur. On the other hand, when the temperature of the heating roll is low, the shrinkage can be suppressed, but the adhesiveness between the base sheet and the film is lowered. According to the method of this example, the adhesiveness between the base sheet and the film can be improved even under low temperature conditions where shrinkage is unlikely to occur.

(3) Transparency Using each laminated sheet and container obtained above, the total light transmittance (Tt) (%) and diffuse transmittance (Td) (%) were measured according to JIS K 7136. . Using the measured Tt and Td, the haze value was calculated based on the following formula. The results are shown in Table 2 and FIGS. 4 and 5.
Haze value (%) = 100 x Td/Tt

From Table 2 and FIG. 4, the total light transmittance of the laminated sheet obtained by pressing once at a roll temperature of 130° C. to 150° C. was less than 85%. On the other hand, the laminated sheets obtained by pressing twice at a roll temperature of 130° C. to 150° C. or pressing three times at a roll temperature of 120° C. to 150° C. all had a total light transmittance of 85% or more. Further, from Table 2 and FIG. 5, the laminated sheet obtained by pressing twice at a roll temperature of 130° C. to 150° C. or pressing three times at 120° C. to 150° C. has a haze value of 6.0% or less. , the same level of haze value was maintained as in the case of pressing once at a roll temperature of 130°C to 150°C. These results show that a laminated sheet with excellent transparency can be obtained by pressing twice at a roll temperature of 130°C to 150°C or pressing three times or more at a roll temperature of 120°C to 150°C.

In addition, in the laminated sheet that was crimped 1 to 3 times or more at a roll temperature of 90 ° C. to 110 ° C. or 1 to 2 times at 120 ° C., the base sheet and film were not bonded, while the roll temperature was 160 ° C. or higher. As a result, the film and/or sheet was deformed, and transparency could not be evaluated.

Further, a molded product was obtained by thermoforming the laminated sheet obtained by pressing twice at a roll temperature of 130°C to 150°C or pressing three times or more at a roll temperature of 120°C to 150°C. Then, as shown in Table 2, the same degree of transparency and haze value as the molded product obtained by thermoforming the laminated sheet obtained by pressing once at a roll temperature of 130 ° C. to 150 ° C. is maintained. there is Biaxially stretched PET films, which are often used as flexible packaging materials, are stretched and heat-set, and it is known that it is difficult to form a laminated product into a container. On the other hand, the shrink film used in this example has a low draw ratio, is amorphous polyester, and does not crystallize, so that it is possible to form a container even after lamination. In addition, as described above, according to this example, it is possible to suppress the occurrence of shrinkage or wrinkles during lamination due to the use of the shrink film while improving the adhesiveness between the base sheet and the film. . From these results, the laminated sheet of this example can be secondary processed (container molding) while suppressing the occurrence of shrinkage during lamination, and it is possible to obtain a molded product that maintains transparency. It turns out that it is possible.

Claims (4)

In a polyester-based laminated sheet in which a polyester-based film is directly laminated on a polyester-based base sheet,
The polyester base sheet is an unstretched amorphous polyester resin,
The polyester film is an amorphous polyester film having a draw ratio of 2 to 7 times in each of the longitudinal and transverse directions ,
The peel strength between the polyester base sheet and the polyester film is 0.98 N or more when measured under the following measurement conditions, the haze value of the laminated sheet is 5.0% or less, and the total light A polyester laminated sheet characterized by having a transmittance of 85% or more.
(Measurement conditions for peel strength)
According to JIS Z 0238, a test piece with a width of 15 mm is peeled at a peel speed of 300 mm/min and a peel angle of 180° to measure the peel strength. 2. The polyester-based laminated sheet according to claim 1, wherein the polyester-based base sheet and the polyester-based film are laminated by thermocompression bonding. A molded article obtained by thermoforming the polyester-based laminated sheet according to claim 1 or 2. A polyester film which is an amorphous polyester film having a draw ratio of 2 to 7 times in the vertical and horizontal directions is directly placed on a polyester base sheet which is an unstretched amorphous polyester resin. obtaining a laminate;
A step of bonding the polyester base sheet and the polyester film by pressing the laminate twice at a roll temperature of 130° C. to 150° C. or three times at a roll temperature of 120° C. to 140° C.;
A method for producing a polyester-based laminated sheet, comprising:

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