JPH0466695B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a reinforced laminate by laminating a reinforcing sheet made of a multilayered thermoplastic resin to various base materials. More specifically, we will develop reinforced laminates with high adhesive strength and excellent performance without using adhesives.
The invention relates to a method for industrially manufacturing the product using simple steps and at low cost. In recent years, various composite materials have been developed in which thermoplastic resin sheets, films, etc. are bonded to base materials such as metal foil, paper, and cloth. Widely used as an expensive material. Furthermore, the performance required for these composite materials varies depending on the purpose of use. Conventionally, most of the manufacturing methods for these composite materials involve a process of bonding the thermoplastic resin and the base material.
Dry lamination methods that use various adhesives, extrusion lamination methods that use anchor coating agents, molten resin, etc., have been adopted. However, these methods increase the cost due to the use of adhesives, or increase the complexity and scale of the equipment.
Furthermore, depending on the type of adhesive, problems such as contamination of the working environment remain. As a method to solve such problems, the present inventors first manufactured a laminate by laminating a sheet (film) of thermoplastic resin A to a base material such as paper, cloth, metal plate, metal foil, etc. In this process, a layer of thermoplastic resin B having a melting point (or softening point) lower than that of thermoplastic resin A is provided on the surface of the sheet that contacts the base material, and the surface of thermoplastic resin B is subjected to corona discharge. The surface tension (γc) is increased to 42 dynes/cm or more by treatment, and the sheet and the base material are laminated with a layer of thermoplastic resin B interposed therebetween, and the melting point (or softening point) of thermoplastic resin A is We have proposed a method of pressure bonding at a temperature lower than the melting point (or softening point) of thermoplastic resin B (Japanese Patent Application Laid-open No. 106583/1983), and have achieved great results. However, even in the above method, manufacturing conditions such as the type of substrate, conditioning of the substrate, temperature conditions during crimping, processing speed, and pressing force during crimping are very limited, and it is difficult to achieve high adhesive strength. It is difficult to produce laminates faster and more uniformly on an industrial scale. Furthermore, in order to increase the surface tension of the substrate, it is necessary to increase the capacity of the corona discharge treatment device or the number of devices, which not only complicates the device but also increases manufacturing costs. In view of the above points, the present inventors have conducted further intensive research in order to obtain a laminate with high adhesive strength using a simple device, at low cost, and on a high-speed industrial scale. , has completed the present invention. That is, the present invention provides a method for manufacturing a reinforced laminate in which a reinforcing sheet is bonded to a base material, in which the reinforcing sheet is made of a thermoplastic resin A and a thermoplastic resin B having a lower melting point (or softening point) than that of the reinforcing sheet. constituted by a multilayer body consisting of at least two layers, and
Before laminating the base material and the reinforcing sheet, at least the surface of the reinforcing sheet is maintained at a temperature range from 50°C to the melting point (or softening point) of the thermoplastic resin B, and the thermoplastic resin B of the reinforcing sheet is The surface tension of the surface is
After applying corona discharge treatment to 42 dynes/cm or more, the base material and the thermoplastic resin B side are bonded,
Next, there is provided a method for manufacturing a reinforced laminate, characterized in that the pressure bonding is carried out in a temperature range from the melting point (or softening point) of thermoplastic resin B to the melting point (or softening point) of thermoplastic resin A. Thermoplastic resin A constituting the reinforcing sheet of the present invention
As the resin, a resin having crystallinity and whose molecules can be oriented by stretching or the like is preferable. For example, high-density polyethylene (including an ethylene-α-olefin copolymer whose density is in the same range as high-density polyethylene and whose main component is ethylene), isotactic polypropylene (a crystalline copolymer whose main component is propylene), ), nylon, polyethylene terephthalate, and other homopolymers, copolymers, and mixtures thereof, or mixtures of these with other resins. On the other hand, the thermoplastic resin B must have a melting point (or softening point) lower than that of the thermoplastic resin A, and must be able to be easily thermocompression bonded to the material at a temperature equal to or higher than the melting point (or softening point). Various resins having such properties can be selected depending on the combination with the thermoplastic resin A, but preferably low density polyethylene, amorphous ethylene-propylene copolymer,
Modified or unmodified homopolymers and copolymers such as ethylene-vinyl acetate copolymer, polyvinyl chloride (soft), polyvinylidene chloride, polymethyl methacrylate, polystyrene, polyolefins modified with maleic acid, acrylic acid, etc. , and mixtures thereof, or mixtures containing these as main components with other resins, etc. are used. Examples of common combinations of thermoplastic resin A and thermoplastic resin B include high-density polyethylene and low-density polyethylene, high-density polyethylene and ethylene-vinyl acetate copolymer, isotactic polypropylene and amorphous ethylene- propylene copolymer,
Examples include a mixture of isotactic polypropylene and polypropylene containing low density polyethylene as a main component. Furthermore, the reinforcing sheet made of a multilayer body of thermoplastic resin according to the present invention is not limited to a two-layer sheet made of a combination of two types of resins each having a different melting point (or softening point). It also includes a multilayer film of three or more layers composed of the same or different resins, which can be pressure-bonded within a temperature range without losing properties (such as stretchability). The reinforcing sheet in the present invention is a two-layer (or multilayer) film or sheet obtained by laminating the thermoplastic resin A and thermoplastic resin B by coextrusion, or a stretched two-layer (or multilayer) film. Furthermore, woven fabrics, non-woven fabrics, net-like bodies, etc. formed by weaving, knitting, cross-laminating, etc., using stretched films as tapes or yarns are preferably used. In addition, as a base material, Western paper such as kraft paper,
Paper sheets such as Japanese paper and styrene paper and other synthetic papers, metal foils such as aluminum foil, foam sheets such as polystyrene, synthetic resin sheets such as polyethylene terephthalate and other oriented sheets, nonwoven fabrics made of synthetic resin fibers, felt, etc. Among them, the above-mentioned paper sheets are most preferably used because cellulose base materials have good adhesion to reinforcing sheets. In the present invention, before joining the base material and the reinforcing sheet, the surface of the reinforcing sheet is maintained at least in a temperature range from 50°C to the free rotation (or softening point) of the thermoplastic resin B. Thermoplastic resin B
It is necessary to apply a corona discharge treatment to the surface to increase the surface tension to 42 dynes/cm or more. At this time, the conditions of the corona discharge treatment, such as the applied voltage and the treatment speed, differ depending on the type of resin B and the shape and spacing of the electrodes, so they may be appropriately determined each time. As mentioned above, the present inventors are pursuing a method that can provide high adhesive strength at higher speed on an industrial scale, and can be produced evenly and stably using a simple device,
Conducted numerous tests. As a result, we found that the surface tension of the surface treated with corona discharge treatment has a large effect on adhesive performance, and various attempts were made to improve it. That is, while maintaining the surface of the reinforcing sheet in a temperature range of 50°C or higher and lower than the melting point (or softening point) of thermoplastic resin B, preferably in the temperature range of 60 to 100°C, the reinforcing sheet is bonded to the base material. By applying corona discharge treatment to the mating surface of thermoplastic resin B to increase the surface tension to 42 dynes/cm or more, it is possible to provide a reinforced sheet with high adhesive strength, even during high-speed operation. A reinforced laminate can be manufactured uniformly and stably. Also, apply the above method to the base material side in the same way,
The effect can be further enhanced by preheating and corona discharge treatment to increase the surface tension of the substrate to 40 dynes/cm or more. If the preheating temperature of the reinforcing sheet is less than 50°C, the surface tension will decrease when the sheet is run at high speeds (speeds commensurate with commercial production), and there is a risk that product defects may occur due to a decrease in adhesive strength or uneven adhesion. Also, the melting point (or softening point) of thermoplastic resin B
A higher temperature is not preferable because it will interfere with the operation of the device. The method of the present invention involves bonding the treated surfaces of the material and the reinforcing sheet that have undergone the above pretreatment to each other, and increasing the temperature from the melting point (or softening point) of thermoplastic resin B to the melting point (or softening point) of thermoplastic resin A. A strongly bonded reinforced laminate can be produced by pressure bonding in a temperature range of . The laminate produced by thermocompression bonding of a reinforcing sheet and a base material is not only made up of two layers, the reinforcing sheet and the base material, but also three-layered, with the reinforcing sheet as the center layer and base material layers on both sides. It is also possible to produce laminates, three-layer laminates with a base material as the center layer and reinforcing sheet layers on both sides, and multilayer laminates obtained by laminating two and/or three-layer laminates on each other. can. EMBODIMENT OF THE INVENTION Below, embodiments will be described with reference to the accompanying drawings regarding the production of laminates, ie, heavy packaging materials, reinforced paper, etc., in which the method of the present invention is particularly effective. FIG. 1 is a schematic explanatory diagram of the process of carrying out the method of the present invention, and reference numeral 1 indicates a reinforcing sheet in which a layer of thermoplastic resin B is arranged so as to face a base material,
2 is a base material, 3 is a corona discharge device, 4 is a preheating roll, 5a to 5i are guide rolls, 6a, 6b and 7a, 7b are pressure rolls, 8 is a reinforced laminate as a product, and 9 is a preheating device. The reinforcing sheet 1 is preheated to a predetermined temperature by passing through a preheating roll 4 heated with steam or the like, and then treated by a corona discharge treatment device 3. The reinforcing sheet consists of a layer of thermoplastic resin A and thermoplastic resin B, and is subjected to electrical discharge treatment so that the surface tension of the surface of thermoplastic resin B on the side to be bonded to the base material is 42 dynes/cm or more. give On the other hand, after the base material 2 also passes through a preheating device (not shown), the surface tension of the bonding surface is reduced by a corona discharge device 3.
At 40 dynes/cm or more, merge and overlap with the reinforcing sheet 1 above. Thereafter, if necessary, the pressure rolls 6a, 6 are preheated by another preheating device 9.
The reinforced laminate 8 as a product is manufactured by further heat-pressing the base material 2 and the reinforcing sheet 1 at a predetermined temperature using steps b, 7a, and 7b. During the above-mentioned heat and pressure bonding, sometimes an adhesion phenomenon occurs between the reinforcing sheet 1 and the pressure bonding roll 7b,
After crimping, the reinforcing sheet 1 sticks to the roll 7b,
The sheet and the base material may partially peel off.
In order to solve this problem, it is preferable to lower the temperature of the roll 7b with which the reinforcing sheet 1 comes into contact with the reinforcing sheet 1 as much as possible. Roll 7b may be cooled if necessary to prevent sticking phenomena. Further, it is desirable to use a roll made of a material such as rubber or synthetic resin having an elastic surface so as to press the reinforcing sheet and the base material over as wide a contact surface as possible as the roll 7b. If the physical properties of the surface material of the reinforcing sheet and the roll 7b to be crimped are similar, there is a risk that the above-mentioned adhesion phenomenon may occur between the reinforcing sheet and the roll 7b. It is desirable to use rubber or synthetic resin with a cohesive energy density (CED) of 40 cal/cc or less. Typical examples of such substances include silicone rubber and polytetrafluoroethylene resin. There is no particular restriction on the pressure of the rolls during crimping as a means of helping the base material and the sheet come into close contact. Further, the arrangement of the pressure rolls is not limited to the apparatus shown in FIG. 1, and one or more pairs of rolls may be provided after the rolls 6a and 7a, if necessary. Note that if thermocompression bonding is possible using only the pressure bonding roll group, preheating by the preheating device 9 is not necessarily necessary. The embodiments of the present invention have been described in detail above, but
The manufacturing method of the present invention is not limited to the above-described embodiments, and the pressurizing method is not limited to rolls, and any device such as a press plate can be used. In the conventional manufacturing method of laminates by thermocompression bonding, net-like bodies, cross bodies, or nonwoven fabrics made of stretched tapes, yarns, etc. undergo significant heat shrinkage at the softening temperature during crimping, making it difficult to bond them well to the base material. However, many problems remain, such as the stretching effect is almost lost, the strength is significantly increased, the equipment is complicated, and the working environment is contaminated. In addition, it has been known to bond split fiber nonwoven fabrics made from stretched multilayer films to kraft paper to make a laminate, but this type of laminate does not have sufficient adhesive strength after pressure bonding and is difficult to peel off. There is a risk of this happening. As mentioned above, the effects of the present invention are particularly significant in the production of heavy packaging materials, reinforced paper, and the like. The present invention has the following advantages when compared with commonly used conventional processing methods such as extrusion lamination or dry lamination using an adhesive. (A) There is no need for adhesives, so costs for equipment and materials can be reduced. (B) The air permeability of the paper is not impaired. (C) After the product is wound up, the adhesive will not run through the mesh and cause blocking. (D) When manufacturing food packaging materials, no hygienic problems occur because adhesives and the like are not used. (E) Problems such as environmental pollution caused by solvent vapor during the adhesive application process do not occur. (F) Despite not using adhesives (auxiliary) agents, it does not require high temperatures like extrusion lamination, so even if a stretching tape is used, the stretching effect is not impaired. The present invention has many advantages as described above, and these advantages exhibit great advantages in industrial implementation. In addition, the reinforced laminate produced by the method of the present invention can be used as a reinforcing sheet, for example, using a split-woven nonwoven fabric of high-density polyethylene/low-density polyethylene (trade name: Nisseki Warif, manufactured by Nippon Petrochemicals Co., Ltd.). When used, kraft paper/warif (heavy packaging material used for fertilizers, etc.), aluminum foil/warif (food packaging material), o-PET (oriented polyester sheet)/warif (material for electric wires), felt/ It can be used in many fields such as water-containing polymers/felt/warif (water-absorbing materials such as diapers), filters, cement curing sheets, and civil engineering materials. The present invention will be further explained below using experimental examples. Experimental Examples 1 to 5 Reinforced laminates were manufactured using the apparatus shown in FIG. Split fiber nonwoven fabric (product name: Nisseki Warif HS, manufactured by Nippon Petrochemical Co., Ltd., glue layer (LDPE)/stretched body (HDPE)/glue layer (LDPE) as a reinforcing sheet
When laminating a three-layer structure (thickness: 70μ, area weight: 35 g/m ² ) and kraft paper (manufactured by Oji Paper Co., Ltd., area weight: 75 g/m ² ), the reinforcing sheet was preheated at various temperatures. After carrying out corona discharge treatment by changing the method, thermocompression bonding was performed, and the peel strengths of the obtained laminates were compared. The results are shown in Table 1. The lamination conditions and test method are as follows. Corona discharge treatment conditions Applied voltage: 190V, Anode current: 0.5A Line speed: 50m/min Crimping temperature: 120℃ Pressing force: 4Kg/cm ² Peel strength: Using Tensilon, for a 25mm wide sample, tensile speed 50mm/min This is the average value of 10 samples obtained by performing a 180° peel test in minutes. Surface tension: Based on ASTM-D2578, this is a measured value of the wet state using a standard liquid formamide-ethyl cellosolve mixture. As shown in the test results in Table 1, it can be seen that when the preheating temperature of the reinforcing sheet is set to 50° C. or higher, a laminate with high surface tension immediately before thermocompression bonding and without peeling can be obtained. 【table】

[Brief explanation of drawings]

FIG. 1 is a schematic illustration of a manufacturing process for testing the method of the present invention. DESCRIPTION OF SYMBOLS 1... Reinforcement sheet, 2... Base material, 3... Corona discharge treatment device, 4... Preheating roll, 5a-5i...
...Guide roll, 6a, 6b, 7a, 7b...Crimping roll, 8...Reinforced laminate, 9...Preheating device.

Claims (1)

[Claims] 1. A method for producing a reinforced laminate in which a reinforcing sheet is bonded to a base material, wherein the reinforcing sheet is made of a thermoplastic resin A and a thermoplastic resin having a lower melting point (or softening point) than that of the reinforcing sheet. Consisting of a multilayer body consisting of at least two layers of B,
And, before laminating the base material and the reinforcing sheet, at least the surface of the reinforcing sheet is maintained at a temperature range from 50°C to the melting point (or softening point) of the thermoplastic resin B. After corona discharge treatment is applied so that the surface tension of the thermoplastic resin B side is 42 dynes/cm or more, the base material and thermoplastic resin B are
A method for producing a reinforced laminate, which comprises joining the surfaces and then pressure bonding at a temperature ranging from the melting point (or softening point) of thermoplastic resin B to the melting point (or softening point) of thermoplastic resin A. 2. Corona discharge treatment is performed so that the surface tension of the thermoplastic resin side B of the reinforcing sheet becomes 42 dynes/cm or more, and corona discharge treatment is performed so that the surface tension of the base material surface becomes 40 dynes/cm or more. 2. A method for manufacturing a reinforced laminate according to claim 1, which comprises performing the following steps. 3. Claim 1 or 2, wherein the base material is any material selected from the group of paper materials, metal foils, synthetic resin sheets, nonwoven fabrics, and felts.
A method for producing a reinforced laminate as described in 2. 4 Thermoplastic resin A constituting the reinforcing sheet
The method for producing a reinforced laminate according to any one of claims 1 to 3, wherein the reinforced laminate is made of a woven fabric, a nonwoven fabric, or a net-like body made of a stretched thermoplastic resin body.