JPH0811432B2 - Shrinkable composite sheet - Google Patents

Description

The present invention relates to a composite sheet composed of a nonwoven sheet and a film.

The composite sheet has heat-shrinkability, is excellent in decorativeness, a close-packing device, and protects against physical damage, and can be used as a shrinkable label for various containers such as soft drinks and sake, and a shrinkable packaging material.

[Conventional technology]

Shrinkable labels using shrinkable films are used as packaging materials for containers and the like.

The shrinkable film is excellent in closely packing the object to be packaged, but is easily broken when scratched by a notch or the like, and is not sufficient for protecting a package such as a bolt.

It has been proposed to use non-woven sheets to remedy the aforementioned problems of shrinkable films. (Japanese Patent Laid-Open No. 61-21364) In that respect, the non-woven sheet is not easily torn even if a notch is inserted therein, and is extremely excellent in terms of protection against physical damage. But,
Since there is a gap between the fibers as compared with the shrink film, the adhesion to the object to be packaged may be slightly inferior.

[Problems to be solved by the invention]

It is an object of the present invention to provide a shrinkable composite sheet which is excellent in tight wrapping property, is hard to be broken by a notch or the like, and is excellent in protecting against physical damage.

[Means for solving problems]

The present invention provides a thermoplastic film having a latent shrinkage rate of 10% or more with a nonwoven sheet having a crystallization index of 15% or more and 45% or less and a latent shrinkage rate of 10% or more as a main component. Of the shrinkable composite sheet adhered to at least one surface of the composite sheet, and it is preferable that at least one of the composite sheets has a heat shrinkability of 10% or more at a temperature of 80 ° C. or higher and 200 ° C. or lower. Further, for labels such as bottles, it is preferable that one side has a latent shrinkage of 20% or less, and the latent shrinkage in a direction orthogonal thereto is 20% or more, which is anisotropic shrinkability.

What is required for the non-woven sheet and the film in the composite sheet is that each has a latent shrinkage rate of 10% or more.

If the latent shrinkage ratio is 10% or less, it does not sufficiently adhere to the shape of the object to be packaged, and thus the object of the present invention is not met.

When the polyester constituting the nonwoven sheet has a crystallinity index of less than 15%, it is deteriorated by heat treatment of heat shrink packaging and discoloration occurs. On the other hand, if the crystallinity index exceeds 45%, it is difficult to obtain a latent shrinkage of 10% or more, and the shrinkability is poor. Also, the wear resistance is poor.

Hereinafter, the nonwoven sheet used in the present invention will be described in detail.

Polyester constituting the non-woven sheet is produced by a known polymerization method, polyethylene terephthalate, or
It is a copolyester mainly composed of repeating units of ethylene terephthalate. It can stably produce a semi-drawn yarn that is substantially amorphous at a second-order transition temperature of room temperature or higher and is crystallized by heat treatment. Is a polymer that can be. In particular, polyethylene terephthalate is preferable in terms of thermoformability, heat resistance of the molded product, strength and the like.

Further, additives usually used for the polyester, for example, pigments, matting agents, antistatic agents, flame retardants, reinforcing particles and the like may be contained. Further, the degree of polymerization is not particularly limited as long as it is within the range for ordinary fiber formation, and a small amount of a polymer such as nylon or polyolefin is mixed within a range not impairing the object of the present invention. Is also possible.
Further, by means of composite spinning, composite fibers such as sheath core and laminating may be used.

The nonwoven sheet used in the present invention can be obtained by a known spunbond method or the like. That is, spinning speed 1600-4000
At m / min, latent shrinkage is 10% or more, breaking elongation is 100% or more,
A semi-stretched polyester continuous fiber web with a birefringence of 0.01 to 0.07 is used at a temperature above the secondary transition point and below the secondary transition point plus 50 ° C using an embossing roll to achieve partial heat with a compression area ratio of 3 to 40%. After the pressure bonding, the temperature of one heat roll is the second transition point plus 30 ℃ or more, the melting point minus 60 ℃ or less, and the temperature of the other heat roll is the second transition point plus 50 ℃ or less. The resulting non-woven sheet, a pair of calender rolls, at a temperature of the secondary transition point or higher and the secondary transition point plus 50 ° C. or lower, the surface is crushed, and then the resin-processed non-woven sheet, for example, Japanese Patent Application Sho 59-251960, Japanese Patent Application Sho 60-20
No. 341, Japanese Patent Application No. 60-20319, biaxially shrinkable non-woven sheet, or a secondary transition point or more,
Non-woven sheet that is heat-shrinked at a temperature not higher than the secondary transition point plus 50 ° C. and at least one is stretched by 1.3 to 2.5 times, using a pair of hot embossing rolls, one of the heat roll temperatures is at least the second transition point, Melting point minus 60 ° C. or less, the other heat roll temperature is secondarily transferred plus 50 ° C. or less and then partially thermocompression-bonded again, and then a non-woven sheet stretched 1.3 to 2.5 times, for example, Japanese Patent Application No. 60-8314. An anisotropic shrinkable nonwoven sheet having a high shrinkability in the uniaxial direction disclosed in Japanese Patent Application No. 61-156286 can be used.

The weave of the nonwoven sheet is 30 denier or less, preferably 0.5 to 10 denier.

The basis weight of the non-woven sheet is preferably 10 to 300 g / m ² .

Further, the non-woven sheet may be laminated or mixed with polyester-based long fibers having different degrees of stretching and weaving.

In addition, what is necessary for producing the non-woven sheet is that the abrasion resistance of the surface is class B or higher under the condition that the latent shrinkability is not 10% or less. If necessary, a calender roll or the like may be used to smooth the surface to improve printability.

If necessary, the surface of the non-woven sheet can be subjected to resin processing, addition of pigments, dyes, etc., printing processing and the like.

As the shrinkable thermoplastic film used in the present invention, polyvinyl chloride resin, polyolefin resin, polyester resin, polystyrene resin and the like are preferably used.

The film to be used must have a latent shrinkage of 10% or more, but a so-called biaxially stretched film that shrinks in both the vertical and horizontal directions, and in either the vertical or horizontal direction. Any so-called uniaxially stretched film that shrinks only can be used.

The thermoplastic film has a thickness of 10 obtained by a known method.
Although the thickness of μ or more can be used, it is preferable to use the thickness of 200 μ or less in terms of processability and cost of the composite sheet.

Next, the adhesion between the above-mentioned nonwoven sheet and the thermoplastic film can be obtained by a method in which an adhesive is applied to the nonwoven sheet or the film with a gravure roll, a kiss roll, a spray, or the like and then bonded. In the bonding step, it is necessary not to disturb the heat shrinkability of the composite sheet. As the adhesive, a two-component reactive urethane adhesive is particularly preferable. Also, a hot embossing roll can be used to partially fuse and bond. In this case, it is also possible to stack them when manufacturing the above-mentioned nonwoven sheet.

 Furthermore, it can be adhered by extrusion lamination.

Incidentally, the combination of the non-woven sheet and the thermoplastic film constituting the composite sheet of the present invention is a material,
The basis weight and thickness can be freely selected.

The composite sheet that shrinks both vertically and horizontally is used for general packaging. A composite sheet that shrinks only in either the vertical or horizontal direction is particularly used for shrinkable labels.

〔Example〕

The present invention will be specifically described below with reference to examples. still,
The definition of the characteristics described in the examples and the measuring method are shown below.

・ Latency shrinkage: Minus melting point of fiber or film
It refers to the shrinkage ratio in at least one direction when heat-treated at a temperature of 20 ° C. or lower for 3 minutes in a free length. In particular,
It is measured at 180 ° C for polyester long fibers, at 135 ° C for polypropylene films, and at 135 ° C for polyvinyl chloride films.

-Heat shrinkage rate: Mark the sample 25 cm x 25 cm at the vertical and horizontal 20 cm positions, heat-treat for 5 minutes in a hot air dryer at the measurement temperature, then take out and measure the dimensional change of the sample to obtain the shrinkage rate.

Birefringence (Δn): Measured under a white light using a polarization microscope pellets compensator.

・ Tear strength (according to JIS L-1096) Take a 5 cm x 15 cm test piece in the vertical and horizontal directions, and
Determined using a tensile tester. (Single tongue method).

-Strength / elongation: (according to JIS-L-1096) Autograph DSS-2000 type universal tensile tester manufactured by Shimadzu Corporation, gripping length 10 cm, tensile speed 20 cm / min, initial load 0.1 g / d, n = The average value of 3 is shown.

・ Shrinkage stress: Using the same measuring machine as the above-mentioned strength and elongation, grasping length
The maximum shrinkage stress at that time is shown in a hot air atmosphere at the measurement temperature in the vertical and horizontal directions of the test piece of 3 cm x 15 cm at 10 cm.

-Crystallinity index The crystallinity index of the 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 goniometer (SG-9R), scintillation counter for measuring tube, wave height analyzer for counting unit,
Cu / Kα rays monochromaticized with a nickel filter (wavelength = 1.
Measure with 5418Å). The fiber sample is set in an aluminum sample holder so that the fiber axis is perpendicular to the X-ray diffraction plane. At this time, the thickness of the sample is set to about 0.5 m / m. Operates X-ray generation at 30KV, 80mA, scanning speed 1 ° / min, chart speed 10mm /
The diffraction intensity is recorded from 35 ° to 7 ° at 2θ in minutes, time constant 1 second, tie divergence slit 1/2 °, receiving slit 0.3 m / m, skitting ring slit 1/2 °. The full scale of the recorder is set so that the diffraction intensity curve is within the scale. Polyethylene terephthalate fiber generally has an equatorial line diffraction angle of 2θ = 17.
It has three major reflections in the range of ° to 26 ° [low angle side (100) (010) (110) plane]. FIG. 1 shows an example of an X-ray diffraction intensity curve of polyethylene terephthalate fiber.
(In the figure, a represents a crystalline 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. 4, the valley near 2θ = 20 ° is set as the apex, and the skirts on the low angle side and the high angle side are connected by a straight line to separate them into a crystalline part and an amorphous part. Ask.

・ Abrasion resistance: Friction tester I for vertical 20 cm × horizontal 3 cm test piece
After rubbing 100 times with a load of 500 g using an I type (Gakushin type), the appearance change of the test piece was judged according to the following judgment criteria and used as a standard for wear resistance.

(Judgment Criteria) Class A There is no eyelash fluff.

Class B: Some fluff but not noticeable Class C: Some fluff is noticeable.

・ Unit weight: Take a test piece of 20 cm x 20 cm, weigh it, and convert it to unit weight.

・ Thickness: Measure at least 3 points using a dial gauge with a load of 100 G / cm ² , and show the average value.

・ Impact resistance: A glass plate with a thickness of 2.0 m / m is placed on a concrete floor, a sample is placed on it, and a steel ball weighing 10 g is dropped from above. The height at which it cracks indicates cushioning.

Example 1 Polyethylene terephthalate having an intrinsic viscosity of 0.72 at a discharge rate of 850 g / min was spun at a melting temperature of 295 ° C. using a rectangular spinneret having a hole diameter of 0.25 mm and the number of holes of 1000, and for traction at a position 1000 mm directly below the spinneret. Spin speed 25 by adjusting the air flow rate of the air heater
It was collected on a wire mesh conveyor at 00 m / min to obtain a long fiber web having a basis weight of 50 g / m ² . (The fiber characteristic of the long fiber web has a birefringence of 0.02.
6, latent shrinkage 58%, crystallinity index 29%, fineness 3.7 denier, breaking elongation 260%. ) Using a pair of embossing rolls having convex portions with a crimping area ratio of 12%, the obtained long fiber web was heated at a temperature of 80 ° C and a linear pressure of
After performing partial thermocompression bonding at kg / cm, perform partial thermocompression bonding again between the upper roll having a textured embossed pattern with a crimping area ratio of 23% and the lower roll with a smooth surface.
C., lower roll 70.degree. C., linear pressure 20 kg / cm to obtain a nonwoven sheet. (Potential shrinkage is 48% in the vertical direction, 43% in the horizontal direction,
The wear resistance of the surface is class A. ) The non-woven sheet obtained is laminated on a polyethylene shrink film (Asahi Kasei Kogyo Co., Ltd., Suntec film, basis weight 48 g / m ² , thickness 0.05 mm, potential shrinkage vertical 53%, horizontal 53%), and the crimp area ratio Between the embossing roll with a pinpoint pattern of 13% and the lower roll with a smooth surface, the non-woven sheet is bonded by thermocompression bonding so that it is in contact with the upper roll. 140 ℃, lower roll temperature 75 ℃, linear pressure 20kg / cm,
The speed is 15m / min. ) A composite sheet of the present invention was obtained. The characteristics of the obtained composite sheet are shown in Table 1.

As a comparative example, a polyester pan bond (E5050 basis weight 50 g / m ² manufactured by Asahi Kasei Kogyo Co., Ltd., latent shrinkage 0%, crystallinity index 55%) was used, and the same polyethylene shrink film as in Example 1 was laminated and the same. A composite sheet was prepared under the conditions. As a comparative example, the characteristics of the polyethylene shrink film are shown in Table 1.

From the results shown in Table 1, the shrinkable composite sheet of the present invention has a latent shrinkage rate of 40% or more both in the non-woven sheet and the film, so that the adhesive surface is uniformly heat-shrinked without peeling. did it. Further, it was found that the tear strength and the impact strength were remarkably high as compared with the film of Comparative Example, and further increased by the heat treatment. On the other hand, the shrinkability of the comparative example is
The shrinkage of the film is restrained by the non-shrinkable non-woven sheet,
In addition, the non-woven sheet became a wavy convex portion at the non-adhesive portion and had an uneven shape. The film of Comparative Example was inferior in tear strength and impact strength as compared with the composite sheet of Example.

Then, using the sheet in Table 1, the heat shrink wrapping property was examined. Cut each of the sheets in Table 1 into a length of 36 cm and a width of 28 cm, and heat them into a bag to form a bag with a length of 10 cm and a width of 20 cm.
Put a 5 cm high rectangular parallelepiped in a bag, and heat sheet the removed part. The obtained package was heat-treated in a hot air dryer at 105 ° C. for 3 minutes to compare the heat shrink wrapping properties.

When making a bag, the non-woven sheet should be placed outside. Also, after heat sealing the four sides, one corner of the bag is about 1 cm
It was cut out and vented.

As a result of the heat treatment, the composite sheet of the present invention had excellent adhesion to a rectangular parallelepiped. On the other hand, in the comparative example, wavy unevenness was formed on the surface and the adhesion was poor.

 The film of the comparative example was excellent in close contact packaging property.

Example 2 Discharge rate using a rectangular spinneret with a hole diameter of 0.25 mm and 1000 holes
Polyethylene terephthalate with an intrinsic viscosity of 0.75 at 850 g / min is spun at a melting temperature of 295 ° C and the spinning speed is adjusted by adjusting the compressed air flow rate of the towing air sacker located 1000 mm directly below the spinneret.
It was collected on a wire mesh conveyor at 2100 m / min to obtain a long fiber web having a basis weight of 80 g / m ² . (Characteristics of constituent fibers: birefringence 0.01
7, latent shrinkage 61%, crystallinity index 19%, fineness 4.2 denier, breaking elongation 310%), the above web crimping area ratio 12%
Using a pair of embossing rolls with
After performing partial thermocompression bonding at a temperature of 20 ° C and a linear pressure of 20 kg / cm, the upper roll temperature is 150 ° C and the lower roll temperature is 90 ° between the pinpoint emboss roll with a compression area ratio of 8% and the roll with a smooth surface. Partial thermocompression bonding was carried out again at a temperature of 15 m / min at ℃, and immediately after that, stretched 1.8 times in the vertical direction with Nippro to obtain an anisotropic shrinkable nonwoven sheet. (Potential contraction rate vertical 14%, horizontal 48
%, Surface abrasion resistance Class A) The obtained non-woven sheet and polyvinyl chloride uniaxially stretched film (Mitsubishi resin, herex film, basis weight 50 g /
m ^2, thickness 0.04 mm, potential shrinkage vertical 6%, horizontal 54%) both were bonded using a two-liquid reaction type urethane adhesive. Adhesive conditions are about 15 g / m ² adhesive applied to the film,
Nonwoven sheets were stacked and pressed to obtain a composite sheet of the present invention. The characteristics of the obtained composite sheet are shown in Table 2.

As a comparative example, a commercially available polyester spun bond (E5080 manufactured by Asahi Kasei Kogyo Co., Ltd., basis weight 80 g / m ² , potential shrinkage 0%, crystallinity index 56%) was used in the same manner as in Example 2, A composite sheet was obtained. In the comparative example, the properties of the polyvinyl chloride film alone are shown in Table 2.

From the results in Table 2, since the composite sheet of the present invention is composed of a non-woven sheet and a film having a latent shrinkage of 20% or less in the vertical direction and a latent shrinkage of 40% or more in the horizontal direction, the adhesive surface No peeling occurred and heat shrinkage was possible. Furthermore, tearing strength,
It was found that the impact strength was remarkably higher than that of the film of Comparative Example and was further increased by the heat treatment.

On the other hand, in the sheet of Comparative Example, the shrinkability of the film is constrained by the non-shrinkable non-woven sheet, and the adhesive surface is partially peeled, and the wavy convex portion in the horizontal direction is formed in the peeled portion, The appearance was poor. The non-woven sheet of the comparative example was inferior in both tear strength and impact resistance.

Then, using the sheet of Table 2, the heat shrink wrapping property was observed. Each of the sheets in Table 2 is cut into a length of 11 cm and a width of 27 cm, and the outer diameter is 8 cm, the height is 15 cm, the upper diameter is 2 cm, and the height is 10 cm to 13 cm.
After stacking two heat sheets in the horizontal direction so that a cylindrical bottle with a slope can be shrink-labeled, put the cylindrical bottle inside and heat-treat it in a hot air dryer at 120 ° C for 3 minutes. The heat shrink wrapping properties were compared.

As a result of the heat treatment, the composite sheet of the present invention could be tightly packed up to the columnar upper inclined portion.

On the other hand, in the sheet of Comparative Example, partial unevenness is formed on the entire sheet, and the contact area with the cylindrical bottle is reduced,
The product was inferior in close wrapping property.

 The film of the comparative example was excellent in close contact packaging property.

From the above, the composite sheet of the present invention can be closely packed to the same extent as the film, and, compared with the film,
It was found that the product had excellent tear strength and impact resistance.

On the other hand, the comparative example did not satisfy the object of the present invention.

[Effects of the Invention] The shrinkable composite sheet of the present invention has heat shrinkability by heat treatment without peeling off the adhesive portion, and is used for shrink wrapping such as a packaged object having an arbitrary shape. It is in close contact with the object to be packaged, is not easily torn even by a notch, etc., and the inclusions can be sufficiently protected against physical damage.

Therefore, it can be used as shrink labels for various containers and shrink wrapping materials.

[Brief description of drawings]

FIG. 1 is a graph showing an example of the X-ray diffraction intensity of polyethylene terephthalate fiber.

Claims (2)

[Claims] 1. A thermoplastic sheet having a latent shrinkage of 10% or more prepared from a non-woven sheet mainly composed of polyester long fibers having a crystallinity index of 15% or more and 45% or less and a latent shrinkage of 10% or more. Shrinkable composite sheet adhered to at least one side of film 2. The shrinkage according to claim 1, wherein the composite sheet has a thermal shrinkage of 10% or more in at least one direction at a temperature of 80 ° C. or higher and 200 ° C. or lower. Composite sheet