JPS6319640B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing reinforced paper by mixing a thermoplastic resin network with paper stock. Specifically, the present invention relates to a method for manufacturing reinforced paper by mixing a thermoplastic resin network with paper stock, and more specifically, a method for producing reinforced paper with excellent performance and a simple process with a large adhesive effect without using adhesives. This invention relates to a method for manufacturing reinforced paper at low cost. Conventionally, reticulated paper has been produced as reinforced paper by moving the reticulated material onto a paper-making screen and mixing it with paper stock, but simply mixing and drying it in this way does not produce the reticulated material. Almost no adhesion occurs between the paper layer and the product easily separates or peels off, making it impossible to obtain a product with practical strength. As a countermeasure to this problem, a method is used in which adhesive is applied to the net-like body in advance in order to improve the adhesion between the net-like body and the paper layer.
Not only is it economically disadvantageous due to the increased cost of the equipment, but depending on the type of adhesive, problems such as contamination of the working environment may occur. The purpose of the present invention is to provide a method for producing mixed reinforced paper that solves the above-mentioned problems. The surface of the thermoplastic resin network in contact with the layer is subjected to a surface treatment such as corona discharge treatment or flame treatment to increase its surface tension (rc) to 42 dynes/cm or more, and then transferred onto a screen to form paper. After mixing with paper, the moisture content is reduced to 15%.
The reinforced paper is dehydrated and dried to a temperature below, and then, just before winding, the reinforced paper is heated to a temperature at which the mesh and the paper layer are thermally fused.
This method involves applying pressure. As described above, the method of the present invention increases the surface tension of the thermoplastic resin network surface to 42 dynes/cm or more before mixing with paper stock, thereby achieving satisfactory strength without using an adhesive. This is based on the discovery that it is possible to obtain mixed reinforced paper with the following characteristics. The thermoplastic resin network used in the present invention is not limited to a single layer structure, and a second thermoplastic resin having a melting point or softening point lower than that of the first thermoplastic resin is disposed on the surface in contact with the paper layer. A multilayer structure consisting of at least two or more types of thermoplastic resins is also possible. In the method of the present invention, reinforced paper is prepared by mixing paper stock and thermoplastic synthetic resin network, dehydrated and dried to a moisture content of preferably 18% or less, and then subjected to pressure treatment under heating. The temperature range varies depending on the raw material of the network, and a temperature range is selected that is above the melting point or softening point of the raw material resin and does not cause thermal deterioration of the network itself. On the other hand, in a multilayer structure, heat and pressure treatment is performed at a temperature range below the melting point or softening point of the first thermoplastic resin and above the melting point or softening point of the second thermoplastic resin that contacts the paper layer. , to form strong adhesion between the paper layer and the net-like body, and to prevent the properties of the first thermoplastic resin (eg, stretching effect, etc.) from being lost. The thermoplastic resin network used in the present invention includes:
A single-layer or multi-layered net-like product obtained by extrusion molding, a stretched product of the obtained net-like product, a single-layer or multi-layer structured film, a sheet, and a stretched product of the obtained film are processed into suitable materials. Examples include woven fabrics, non-woven fabrics, net-like bodies, etc., which are processed into split fibers, tapes, etc. by a method, and then manufactured by methods such as spreading, weaving, knitting, and cross-layering. For the first thermoplastic resin constituting the network, it is desirable to use a resin that has crystallinity and exhibits molecular orientation through stretching, etc. homopolymers, copolymers, and These resins may be used together or mixtures of these resins with other resins may be used. On the other hand, the second thermoplastic resin has a melting point or softening point lower than that of the first thermoplastic resin, and has a temperature above the melting point or softening point at which the properties of the first thermoplastic resin are not impaired by heat. A material that can be easily pressed onto the paper layer within a range is used. Various resins having such properties can be selected depending on the combination with the first thermoplastic resin, but preferred examples include low-density polyethylene, amorphous ethylene-propylene copolymer, and ethylene-vinyl acetate. Copolymers, modified polyolefins modified with polyvinyl chloride (soft), polyvinylidene chloride, polymethyl methacrylate, polystyrene, maleic acid, acrylic acid, etc., unmodified homopolymers, copolymers, and their own or Examples include mixtures containing these as main components and other resins. Examples of common combinations of the first thermoplastic resin and the second thermoplastic resin include high-density polyethylene and low-density polyethylene, high-density polyethylene and ethylene-vinyl acetate copolymer, and isotactic polypropylene and Examples include crystalline ethylene-propylene copolymers, mixtures of isotactic polypropylene and polypropylene mainly composed of low-density polyethylene, and the like. The paper stock used in the present invention means wood pulp, synthetic pulp, or a suitable mixture thereof. Next, an example of an embodiment of the present invention will be described with reference to the accompanying drawings. This figure shows a process diagram of an apparatus for manufacturing reinforced paper mixed with reticulated material using a so-called circular mesh paper machine. After the reticulated material 1 is surface-treated on both sides by corona discharge device 2, , the paper stock is sucked onto one side of the mesh body 1 by the cylinder 3 to form a wet web layer and transferred to the felt 5. On the other hand, a wet web layer similarly formed by the cylinder 4 and the felt 6 is superimposed on the other side of the net 1 on the felt 5, and after being dehydrated to some extent, it is heated to about 100 to 105°C with a hot roll 7. dried at temperature,
Further, it is heated to a predetermined temperature, for example, 120° C., by a heat roll 8, and paper layers are pressed onto both sides of the net-like material 1, thereby completing the intended reinforced paper mixed with the reticulated material. However, the present invention is not limited to the above-mentioned embodiments; for example, a fourdrinier paper machine may be used instead of the circular wire paper machine, and heating and pressure treatment may also be performed using
In addition to the above methods, it is also possible to use other methods commonly used for heating and pressurizing. According to the above-mentioned method for producing mixed reinforced paper of the present invention, no adhesive is required compared to conventional production methods, so it is not only economically advantageous in terms of raw materials and equipment, but also The problem of environmental pollution is also eliminated, and there is no risk of hygienic problems even when the product is used in food packaging. The present invention will be specifically described below with reference to Examples. Examples 1 to 2 High-density polyethylene (hereinafter abbreviated as HDPE) (MI1.0, density 0.956, melting point 129°C) is used as the center layer (first thermoplastic resin), and low-density polyethylene (hereinafter referred to as (abbreviated as LDPE)
(MI3.0, density 0.923, melting point 109℃) layer (second thermoplastic resin) was formed by coextrusion, and the resulting three-layer film with a width of 1500 mm and a thickness of 0.13 mm was
1 which is uniaxially stretched and has a width of approximately 530 mm and a thickness of approximately 0.05 mm.
An axially stretched membrane was obtained. This is split by sliding it in contact with a rotary splitting tool, and the resulting split fiber network with a continuous structure is developed into continuous split fibers with a width of approximately 1400 mm, which are then laminated in the warp and warp to have a basis weight of approximately 35 g/ A split fiber nonwoven fabric of m ² was produced. In accordance with the method shown in the accompanying drawings, this was subjected to double-sided corona discharge treatment at a line speed of 35 m/min, and the surface tension was varied by changing the applied voltage, mixed with paper stock, and heated roll 7 ( After drying to a moisture content of 15% at a temperature of 105℃, heat roll 8 (temperature of 120℃)
The paper was heat-pressed using Rubber Nipprol 9 (linear pressure 7 kg/cm) to produce a reinforced paper with a mesh material having a basis weight of approximately 175 g/m ² . Table 1 shows the results of a peel strength test conducted on the obtained reinforced paper mixed with a reticulated material. Example 3 Reticulated reinforced paper was produced in exactly the same manner as in Example 1, except that low-density polyethylene was replaced with ethylene-vinyl acetate copolymer (hereinafter abbreviated as EVA), and the results of the peel strength test were are shown in Table 1. Comparative Examples 1 to 3 A split fiber nonwoven fabric of low density polyethylene that was exactly the same as in Example 1 was used with a surface tension of 42, which is an essential requirement of the present invention.
Table 1 shows the results of the peel strength test of the resulting reticulated reinforced paper, which was subjected to corona treatment so as to obtain a surface tension outside the range of dynes/cm or more.

Measurement of [Table]. )

[Brief explanation of the drawing]

The drawings show an example of the manufacturing process of the present invention using a circular mesh paper machine. 1... Reticular body, 2... Corona discharge device, 3, 4
...Cylinder, 5, 6...Felt, 7, 8...
...Heat roll, 9...Rubber nip roll, 10...
Reinforced paper, 11, 12...Paper stock tank.

Claims (1)

[Claims] 1. In a method for producing reinforced paper by mixing a thermoplastic resin network and paper stock, the surface that will come into contact with the paper layer is subjected to a surface treatment such as corona discharge treatment or flame treatment in advance. The reticulated material with a surface tension (rc) of 42 dynes/cm or more is mixed with paper stock and dried until the moisture content is at least 20% or less to make reinforced paper. 1. A method for producing mixed paper reinforced paper, which comprises heating and pressurizing the thermoplastic resin to a temperature equal to or higher than the melting point or softening point of the thermoplastic resin immediately before winding. 2. The structure of the reinforced paper is a multilayer structure composed of at least two or more types of thermoplastic resins, in which a second thermoplastic resin having a lower melting point or softening point than the first thermoplastic resin is in contact with the paper layer. A patent claim characterized in that the temperature at which the reinforcing paper is heated and pressed immediately before winding is below the melting point or softening point of the first thermoplastic resin and above the melting point or softening point of the second thermoplastic resin. A method for producing a reinforced paper mix according to item 1. 3. Claims 1 or 2, characterized in that at least the first thermoplastic resin among the thermoplastic synthetic resins constituting the network body exhibits a stretching effect, and the network body is a stretched body. The method for producing mixed reinforced paper described in . 4. The mixed reinforced paper according to claim 2 or 3, wherein the net-like body is composed of split fibers made from a multilayer film or a warp-warp laminated nonwoven fabric of the split fibers. Production method.