DOUBLE-SIDED ADHESIVE FABRIC-BASED MATERIAL

Abstract: A non-woven fabric support is used, e.g. of viscose rayon, a polyester or polyolefin, which has pores at least 50% of which penetrate through the fabric, the proportion of the area of the penetrating pores per area of the fabric being at least 20%, the average opening area of the penetrating pores being at least 0.001 mm², and the weight of the fabric is 50 g/m² or less. The fabric may be resin treated. A single coating of a pressure-sensitive adhesive (e.g. acrylic or rubber-based) solution or aqueous dispersion is formed on the inside or both sides of the fabric to a solids content of 10 - 300 g/m², and the coating is dried. The resultant double sided adhesive tape has uniform thickness and does not delaminate or suffer gapping.

Description: The present invention relates to a double-­ sided adhesive tape, sheet or leaf having a pressure-­ sensitive adhesive layer on both sides thereof (hereinafter referred to as "double-coated adhesive tape" for simplicity), and more particularly, to a double-coated adhesive tape which is free from de­ lamination and has a uniform thickness obtained by a single coating of a pressure-sensitive adhesive solution or aqueous dispersion on a thin non-woven fabric as a tape support, whereby the pressure-sensitive layers on both sides of the thin non-woven fabric are in­ tegrally bonded. In general, double-coated adhesive tape is prepared by forming a pressure-sensitive adhesive layer on both sides of a tape support such as a paper, a non-woven fabric, a film or sheet of a foamed product, a plastic film, etc. Those tape supports have fine pores or do not entirely have pores. Therefore, in order to form a pressure-­ sensitive layer on both sides of the support, a pressure-sensitive adhesive solution or aqueous dispersion must be coated on both sides of the tape support respectively. The double-coated adhesive tape using a tape support having cushioning properties such as a paper, a non-woven fabric, a film or sheet of a foamed product, which are conventionally used, exhibits good adhesive properties to an object to be adhered even if the surface thereof is a rough surface, due to the cushioning properties of the tape support. On the other hand, such double-coated adhesive layers provided on both sides of the tape support are sepa­ rated by the tape support, in the event that the adhesive tape is rapidly unwound from a tape rolled state or an external force is applied to an object adhered with the adhesive tape, delamination tends to occur in the tape support, and also where the adhesive tape is wound into a rolled state by inter­ posing a release paper or release film therebetween and stored, the pressure-sensitive adhesive layer partially impregnates into the tape support, and as a result, the thickness of the adhesive tape becomes non-uniform or a so-called gapping occurs, thereby markedly lowering the commercial value. On the other hand, use of a porous tape which has been subjected to a physical perforation treatment is proposed to prevent the delamination. However, since the tape support is thick and the pore intervals are long, the delamination is not effectively prevented. Further, since it is difficult for the pressure-sensitive adhesive layer to be suf­ ficiently charged within the pores at the preparation, the pressure-sensitive adhesive layer is pressed into the pores with the passage of time and such portions become sunken, markedly deteriorating the commercial value of the tape. Further, in order to prevent non-uniformity of the tape thickness due to impregnation or gapping, an attempt has been made that no tape support is used and the adhesive function is produced by the pressure-sensitive adhesive layer. However, a pressure-sensitive adhesive layer alone lacks self-­ supporting properties, its handling is difficult and deformation easily occurs during handling and operation. Accordingly, an object of the present in­ vention is to provide a novel double-coated adhesive tape which overcomes the disadvantages encountered in the prior art. The double sided adhesive material according to the present invention comprises a tape, sheet or leaf support having provided on both surfaces thereof a pressure-­ sensitive adhesive layer, wherein the support is a thin non-woven fabric having the following properties: A) pores substantially penetrating from one surface to the other surface are present; B) the total area of the substantially penetrating pores is at least 20%; C) the average opening area of the sub­ stantially penetrating pores is at least 0.00l mm²; and D) its weight is 50 g/m² or less. In the accompanying drawing: The Figure is a cross-sectional view of an embodiment of the double-coated adhesive tape according to the present invention. In the Figure, 1 is a thin non-woven fabric having through pores 3 and partial pores 4 as a support, and 2 is a pressure-sensitive adhesive layer formed on both sides of the non-woven fabric and within the pores thereof. The double-coated adhesive tape according to the present invention is prepared using, as a tape support, a thin non-woven fabric having the following specific structures and weight: A) Pores substantially penetrating from one surface to other surface are present; B) The total area of the substantially penetrating pores is at least 20%; C) The average opening area of the sub­ stantially penetrating pores is at least 0.00l mm²; and D) The weight is 50 g/m² or less. In the preparation of the double-coated adhesive tape, a pressure-sensitive adhesive solution or aqueous dispersion having a viscosity(at 25°C) of about several tens to several hundred poises is used. The double-coated adhesive tape according to the present invention can be prepared by a method comprising coating the pressure-sensitive adhesive solution or aqueous dispersion on, for example, a release paper, placing the tape support on the coating layer, thereby embedding the tape support in the coating layer, and drying the assembly under heating under this state. The double-coated adhesive tape can also be prepared by a method comprising coating the pressure-­ sensitive adhesive solution on a release paper, laminating the tape support on the coating layer, coating the pressure-sensitive adhesive solution or aqueous dispersion on the tape support, and drying the assembly under heating under the condition that the support is impregnated with the solution or aqueous dispersion. Therefore, the thin non-woven fabric used as the tape support must be sufficiently porous to the extent that the pressure-sensitive adhesive solution or aqueous dispersion can pass through the tape support easily and quickly within a short period of time. The porous conditions of the tape support are as follows. A) At least 50% of pores of the thin non-­ woven fabric substantially penetrate the thin non-­ woven fabric. The expression "substantially penetrate" means the portion that fibers are not entirely present, assuming that the non-woven fabric is planar. B) The proportion of the area of the penetrating pores (i.e., the proportion of the area of the penetrating pores per unit area of the non-­ woven fabric) is at least 20%, preferably 30 to 90%, and most preferably 50 to 80%. If the proportion thereof is less than 20%, the pressure-sensitive adhesive solution or aqueous dispersion does not pass or is difficult to pass through the thin non-woven fabric; as a result, the integral bonding of the pressure-sensitive adhesive layers on both sides of the thin non-woven fabric is not effective, resulting in delamination. C) The average opening area of the sub­ stantially penetrating pores is at least 0.00l mm², preferably 0.005 to 0.5mm², and most preferably 0.0l to 0.2 mm². If the average opening area is less than 0.00l mm², the integral bonding of the pressure-­ sensitive adhesive layers is not effective due to non-passing of the pressure-sensitive adhesive solu­ tion or aqueous dispersion through the non-woven fabric. D) The weight of the thin non-woven fabric is 50 g/m² or less, preferably 2 to 25 g/m², and most preferably 5 to l5 g/m². If the weight thereof exceeds 50 g/m², the proportion of the opening area of the pores becomes too small or the thickness of the non-woven fabric becomes too thick, and the pressure-sensitive adhesive solution or aqueous dispersion does not pass through the non-woven fabric sufficiently. Another fabric condition is the thickness of the non-woven fabric. The thickness thereof is not particularly limited, but it is preferred for the thickness to be 180 µm or less. A smaller thickness of the non-woven fabric is preferred in that the amount of the pressure-sensitive adhesive can be decreased and foaming is difficult to occur; however, the physical strength then is poor, so the thick­ ness of 5 to 80 µm is preferred from the standpoint of the practical use. The porous thin non-woven fabric is pre­ pared using fibres made of, for example, viscose rayon, a polyester or polyolefin. The double-coated adhesive tape according to the present invention is prepared by a single coating of a pressure-sensitive adhesive solution or aqueous dispersion in the inside or on both sides of a porous thin non-woven fabric in an amount such that the solids content of the adhesive solution or aqueous dispersion is about l0 to about 300 g/m², so that the non-woven fabric is impregnated with the solution of aqueous dispersion, thereby forming substantially non-porous pressure-­ sensitive adhesive layers on both sides of the non-­ woven fabric. The pressure-sensitive adhesive which can be used in the present invention is generally an acrylic pressure-sensitive adhesive or a rubber-­ based pressure-sensitive adhesive. Examples of the acrylic pressure-sensitive adhesive include acrylic copolymers prepared by copolymerizing alkyl esters of (meth)acrylic acid and monomers copolymerizable therewith (e.g., (meth)­ acrylic acid, (meth)acrylic acid-2-hydroxyethyl ester, (meth)acrylamide, glycidyl (meth)acrylate, vinyl acetate, acrylonitrile, styrene or vinyl pyrrolidone). Examples of the rubber-based pressure-­ sensitive adhesive include mixtures of rubbers (e.g., natural rubber, polyisobutylene rubber, chloroprene rubber, styrene-isoprene-styrene block copolymer) and tackifiers (e.g., resin, terpene resin or petroleum resin). The non-woven fabric may, before the adhesive coating, be subjected to a resin treatment by coating a solution (solids content: 2-7 wt%) of a resin having a modulus of elasticity of at least l0³ kg/cm², preferably at least 5 × l0³ kg/cm², such as polystyrene a polyacrylic ester or polyvinyl chloride, dissolved in a solvent, and drying the resulting coating. The amount of resin treatment on the non-­ woven fabric (i.e., the amount of resin deposited) is determined depending upon the weight and quality of the non-woven fabric, modulus of elasticity of the resin, and the like. For example, in a rayon-­ based non-woven fabric or synthetic fiber-based non-­ woven fabric having an average pore area of 0.l - ­ 0.0l mm², a proportion of opening pores of 70 - 90% and a weight of 7 to l3 g/m², a polystyrene resin having a modulus of elasticity of l to 20 g/m² is coated thereon in an amount of l to 20 g/m². This resin treatment is more effective to prevent the delamination of the double-coated ad­ hesive tape. The double-coated adhesive tape of the present invention having the structure as described above has the characteristics that since the adhesive layers present on both sides of the thin non-woven fabric are integrally bonded, the tape has uniform thickness, delamination does not occur, and the tape does not suffer gapping with the passage of time. Further, the tape has the practical features that the tape is flexible, can be cut with fingers, and has a self-supporting property, resulting in easy handling.

Claims: 1. A double-sided adhesive tape, sheet or leaf comprising a support having provided on both surfaces thereof a pressure-­ sensitive adhesive layer, wherein the support is a thin non-­ woven fabric having the following properties: A) pores substantially penetrating from one surface to the other surface are present: B) the total area of the substantially penetrating pores is at least 20%; C) the average opening area of the substantially penetrating pores is at least 0.001 mm²; and D) its weight is 50 g/m² or less. 2. A double-sided adhesive material as claimed in Claim 1, wherein the area of the substantially penetrating pores is 30 to 90%. 3. A double-sided adhesive material as claimed in Claim 1 or 2, wherein the average opening area of the substantially penetrating pores is 0.005 to 0.5 mm². 4. A double-sided adhesive material as claimed in Claim 1, 2 or 3, wherein the weight of the thin non-woven fabric is 2 to 25 g/m². 5. A double-sided adhesive material as claimed in any preceding claim, wherein the thin non-woven fabric has a thickness of 180 µm or less. 6. A double-sided adhesive material as claimed in any preceding claim, wherein the support was coated with a solution of a synthetic resin having a modulus of elasticity of at least 10³ kg/cm², before the adhesive was coated.

Inventors: KONISHI, TOSHIHARU NITTO ELECTRIC INDUSTRIALCO.LTD, MORIYAMA, TAKAAKI NITTO ELECTRIC INDUSTRIALCO.LTD, USHIRO, HIROYUKI NITTO ELECTRIC INDUSTRIALCO.LTD
Applicants: NITTO DENKO CORPORATION
Application year: 1987
Main classification: C09J7
IPC codes: C09J7