JP3501230B2 - Base material for craft adhesive tape - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a substrate for a kraft pressure-sensitive adhesive tape. To elaborate further,
The present invention relates to a base material of a release paper of an adhesive tape mainly used for packing of packaging materials and packaging containers, and in particular, an organic solvent containing a release agent such as silicone without directly laminating polyethylene on base paper. The present invention relates to a substrate for a kraft pressure-sensitive adhesive tape to which a solution or a solventless silicone solution can be applied. [0002] Conventionally, in order to improve the releasability of a tape wound in a cylindrical shape, a release agent or a release agent, for example, a solution obtained by dissolving a silicone resin in an organic solvent such as toluene or a solventless type As a substrate for kraft adhesive tape formed by applying a silicone solution, the penetration of the silicone coating liquid is minimized on the surface of kraft stretched paper (hereinafter also referred to as Krupak paper) to maximize the releasability. For the purpose, a polyethylene film layer having a thickness of about 10 to 25 microns is generally formed by an extrusion processing method. However, in the base paper for release paper manufactured by the above-described method of laminating polyethylene, the polyethylene forms a strong continuous film and is insoluble in water. Recycling in the papermaking process is not possible and is a major problem in industrial waste treatment today. On the other hand, Japanese Patent Publication No. 1-35959 and JP-A-4-23876 disclose a base paper as a base material for a release paper obtained by directly applying a silicone solution without laminating polyethylene. There is disclosed a clay coat type substrate in which a coating mainly composed of an inorganic pigment and an organic adhesive is applied to the surface to form an undercoat layer. In such a base material, an undercoat layer covers minute voids (hereinafter, also referred to as pinholes) in the base paper, and the effect of stopping the undercoat layer is recognized. However, the organic solvent solution of the silicone penetrates into the base paper through countless fine continuous holes existing between the pigments of the undercoat layer. For this reason, it is necessary to apply a large amount of expensive silicone compared to the method of laminating with polyethylene, and it is difficult to apply this method to the production of a kraft adhesive tape. Further, Japanese Patent Application Laid-Open No. 4-2900 discloses that
A method of undercoating with starch as a filler is disclosed, but since this starch solution itself is buried in the pinhole, it can serve as a filler for the pinhole having a pore size of 1 to 200 microns or more. For this reason, it is impossible to block the penetration of the silicone organic solvent solution or the solvent-free silicone solution only with the undercoat layer of starch (hereinafter also referred to as solvent barrier property). [0006] For the above reasons, there is a strong demand for a kraft pressure-sensitive adhesive tape base material having a solvent barrier property comparable to that obtained by laminating polyethylene and capable of directly applying an organic solvent solution of silicone. No substrate has yet been provided that can meet these requirements. SUMMARY OF THE INVENTION The present invention does not require a polyethylene laminate, can directly apply an organic solvent solution of silicone or a solventless silicone solution, and exhibits excellent peelability. The purpose of the present invention is to provide a base material for a kraft pressure-sensitive adhesive tape. SUMMARY OF THE INVENTION The present inventors have found that, without laminating polyethylene on clupak paper, it has excellent solvent barrier properties comparable to this, and can be easily disaggregated in water and reused. In order to obtain a possible base material for craft adhesive tape, as a result of analyzing the function of this polyethylene layer in detail for a substrate laminated with polyethylene, it was manufactured using wood pulp as a main raw material and had a pore diameter of 0.1 to
(1) To completely suppress the permeation of the organic solvent solution of silicone into porous and liquid-absorbing clupak paper having fine pores of 1.0 micron, and (2) scattered in the base paper. It has been concluded that forming a barrier layer that can simultaneously achieve pinholes with a pore size of 1 to 200 microns is an effective means. The present inventors have further studied to establish this means, and have found that the barrier layer has a polymerization degree of 200 to 800,
It has been found that it is an effective means to contain a partially or completely saponified polyvinyl alcohol having a saponification degree of 88 to 99.9 mol%, and the present invention has been completed. Therefore, the present invention provides a kraft stretched paper mainly composed of wood pulp specified by JIS P 3412-1976R, and a water-soluble resin formed on one surface of the kraft stretched paper and containing a water-soluble resin as a main component. In a base material for a kraft pressure-sensitive adhesive tape having a barrier layer,
The present invention relates to a kraft pressure-sensitive adhesive tape base material containing a partially or completely saponified polyvinyl alcohol having a saponification degree of from 800 to 88 to 99.9 mol%. [0011] The krupak paper used in the present invention is a coniferous kraft pulp as a main raw material, and is an endless endless paper through a nip roll on a part of a dryer roll of a fourdrinier multi-cylinder paper machine or a fourdrinier Yankee type paper machine. Attach a device that rotates a thick rubber belt by pressing and rotating, pass wet paper between the dryer and the belt, and use kraft stretch paper that contracts using the contraction of the belt that has been stretched in advance, and the longitudinal extension is large. Therefore, it is characterized by high tensile strength and high impact strength. The clupak paper may contain organic and inorganic pigments and chemicals. The degree of polymerization used in the present invention is from 200 to 80.
0, partially saponified or completely saponified polyvinyl alcohol having a saponification degree of 88 to 99.9 mol% exhibits remarkable film-forming properties due to its strong bonding force, and exhibits excellent solvent barrier properties. Further, the polyvinyl alcohol has a function of blocking pinholes having a pore size of 1 to 200 microns scattered in Clupak paper, and has fine voids having a pore size of 0.1 to 1.0 micron. It also exerts the effect of totally suppressing the penetration of the organic solvent solution of silicone or the solvent-free silicone solution into the rich clupak paper. The polyvinyl alcohol used in the present invention is generally referred to as poval. The basic composition is a copolymer of vinyl alcohol and vinyl acetate, and the degree of polymerization and the degree of saponification are decisive factors controlling the properties of polyvinyl alcohol. The degree of polymerization of commercially available polyvinyl alcohol is in the range of 300 to 2500, and it is said that the higher the degree of polymerization, the better the solvent barrier property. However, the present inventors have examined the relationship between the degree of polymerization of polyvinyl alcohol and the solvent barrier property in detail, and as a result, it has been found that a highly porous and highly permeable clupak paper containing wood pulp as a main component is obtained. In the case of forming a barrier layer, in order to minimize the penetration of the barrier layer into the inside of the clupak paper, contrary to the above, a high concentration of polyvinyl alcohol having a low polymerization degree is applied, specifically, polymerization is performed. Polyvinyl alcohol with a degree of 200 to 800
It has been found that coating at a high concentration of 6% by weight is necessary to obtain the desired solvent barrier property. The permeation of the barrier layer is influenced by the concentration and viscosity of the barrier agent, and an increase in the concentration is a necessary condition for suppressing the permeation of the barrier layer. In the case of polyvinyl alcohol having a degree of polymerization exceeding 800, when the concentration of the solution at the time of coating is adjusted to the above range, the viscosity becomes extremely high and the fluidity becomes poor, so that coating is practically impossible. . On the other hand, when the degree of polymerization is less than 200, the viscosity is low and the coating is possible, but the degree of polymerization is low and the film forming property is inferior, so that a desired barrier layer cannot be formed. The degree of saponification, which greatly affects the properties of polyvinyl alcohol, must be 88-99.9 mol% of a partially or completely saponified type, and the degree of saponification is less than 88 mol%. In this case, since the crystallinity is low, the water resistance is poor and the function as a kraft adhesive tape is significantly impaired. Examples of the polyvinyl alcohol that can be used in the present invention include “NL05” commercially available from Nippon Synthetic Chemical Industry and “PVA” commercially available from Kuraray.
105 "etc. correspond to this. There is no strict restriction on the blending ratio of polyvinyl alcohol in the barrier agent, but it is necessary that the total solid content in the barrier agent accounts for 70 parts by weight or more. If the blending ratio is less than this, it is not possible to exhibit the excellent pinhole sealing effect of the polyvinyl alcohol and the effect of totally suppressing the penetration of the silicone solution, and obtain sufficient solvent barrier properties. Becomes difficult. The barrier agent used in the present invention can be applied by mixing other materials with polyvinyl alcohol.
There are no particular restrictions on the materials used in the mixture, and inorganic pigments such as kaolin, talc, calcium carbonate, titanium dioxide, and aluminum hydroxide, and binders such as starch, casein, styrene-butadiene latex, acrylic resin emulsions, and polyacrylamide Can be used as appropriate. Further, a dispersant, a water-proofing agent, a lubricant, an antifoaming agent, a coloring agent, a preservative, and the like can be optionally blended. However, as noted above, these materials need to be less than 30 parts by weight of the total solids in the barrier agent. The barrier agent coating equipment can be arbitrarily selected from a size press, a gate roll coater, a bar coater, a roll coater, an air knife coater, a blade coater and the like. The barrier layer formed on the clupak paper is desirably prepared so as to be applied in an absolute dry weight of 0.5 to 10 g / m ^{2 in} consideration of the filling effect and the price of the paint. The application of polyvinyl alcohol for forming the barrier layer can also be performed on the clupak paper by two or more coating operations. After the above-mentioned polyvinyl alcohol is applied, if necessary, a smoothing treatment may be carried out by using finishing equipment such as a super calender. In this case, the surface quality of the obtained barrier layer is improved, and the silicone coating is applied. It becomes possible to form a work layer uniformly. In this case, the smoothness is set to 20 to 2000 seconds (JAPAN TAP) according to the purpose.
It is preferable to control within the range of Oken type smoothness described in PI paper pulp test method No. 5. As described above, silicone is usually applied by dissolving it in an organic solvent such as toluene or hexane. However, as described above, the barrier layer can exhibit excellent barrier properties to the monomer even by a solventless method in which the silicone and the monomer are mixed and cured by ultraviolet rays or electron beams as described above. The substrate for a kraft pressure-sensitive adhesive tape produced by the method of the present invention has a solvent barrier property comparable to that of a substrate laminated with polyethylene, has excellent defibration properties, and does not require a step of laminating polyethylene. For,
It has the advantage of extremely low manufacturing costs. Further, the kraft pressure-sensitive adhesive tape using the base material of the present invention can be easily subjected to a regeneration step after recovery since there is no polyethylene laminate layer. When the kraft pressure-sensitive adhesive tape is put into water in the regeneration step, the barrier layer is detached from the clupak paper, so that only the pulp can be easily collected and reused. Because this recycled pulp does not contain water-repellent silicone,
Silicone does not enter the papermaking process of printing paper and the like, and does not cause cissing or other obstacles. The present invention will be described in more detail with reference to the following examples, but the scope of the present invention is not limited by these examples. In each example, "parts" indicates "parts by weight of solid content" unless otherwise specified. Example 1 A substrate for a kraft pressure-sensitive adhesive tape was produced by the following steps. (1) Papermaking of base paper First, a stock having the following composition was prepared. Ingredient weight softwood kraft pulp (freeness: 570 ml) 100 parts 30% fortified rosin sizing agent from (SPE, Arakawa Chemical Industries, Ltd.) 0.3 parts 30% aluminum sulfate 2 parts then this stock, the Kurupakku paper processing equipment A base paper having a rice basis weight of 73 g / m ^{2 was} produced by the attached fourdrinier multi-cylinder paper machine. The density of the base paper thus obtained is 0.85 g / c.
m ³ , and the Oken-type smoothness of the contact surface of the base paper with the dryer cylinder was 35 seconds. (2) Formation of barrier layer A coating solution for a barrier layer having the following composition was prepared. Ingredient wt 12% polyvinyl alcohol (polymerization degree: 500, saponification degree 98.5 mol%, NL05, manufactured by The Nippon Synthetic Chemical Industry Co.) 100 parts [0028] The 12% coating solution on dryer cylinder contact surface of the Kurupakku paper 5.0 g / dry weight
m ² and dried. Further, a base material for a craft adhesive tape was prepared by using a super calender with a Wken type smoothness of 260 seconds. A predetermined piece of paper was prepared from the base material for kraft pressure-sensitive adhesive tape, and its toluene permeation preventing effect, pinhole preventing effect, silicone permeation preventing effect, and disintegration after silicone coating were evaluated by the following methods. (1) Toluene permeation preventing effect and pinhole preventing effect: Oil-soluble dye "Olesol"
Toluene colored with "Red B" (manufactured by Sumitomo Chemical Co., Ltd.) was applied, and after 2 seconds, it was wiped off with a gauze, and the permeation state of the toluene on the surface and the effect of pinholes formed in spots were determined. (2) Silicon penetration preventing effect: A silicone solution having the following composition was prepared. Ingredient weight addition reaction type silicone (SD7220, manufactured by Toray Industries) 4.5 part of a platinum catalyst (SRX212, Toray Industries) by Meyer bar to 0.5 parts 95 parts The above solution onto the test piece of paper toluene, bone dry 3.0
g / m ^2, and the resulting surface was observed to evaluate the penetration of silicone. (3) Disintegration after silicone application: The release paper obtained by applying the silicone solution described in (2) above is subjected to disintegration treatment using a standard disintegrator specified in JISP8209, and sample components are obtained. The dispersibility was evaluated by observing the dispersion state of the. Table 1 shows the test results. Example 2 A substrate for a kraft pressure-sensitive adhesive tape was prepared in the same manner as in Example 1, and an evaluation test was performed. However, instead of the base paper of Example 1, base paper made by the following method was used. First, a sample having the following composition was prepared. Ingredient weight bleached softwood kraft pulp (freeness: 570 ml) 50 parts of 30% fortified rosin sizing agent 2 parts (SPE, Arakawa Chemical Industries, Ltd.) 0.3 parts 30% aluminum sulfate [0033] Then from this stock, Kurupakku Rice basis weight 73g / m ² by Fourdrinier multi-cylinder paper machine equipped with paper processing equipment
Base paper was made. The density of the base paper thus obtained was 0.82 g / cm ³ , and the Oken-type smoothness of the rubber roll contact surface was 25 seconds. A barrier layer was formed on the rubber roll contact surface of the clupak paper thus obtained in the same manner as in Example 1. Table 1 shows the test results. Example 3 A substrate for a kraft pressure-sensitive adhesive tape was prepared in the same manner as in Example 1, and an evaluation test was performed. However, instead of NL05 in the coating liquid for barrier layer of Example 1, NL05 / oxidized starch (Oji Ace A, manufactured by Oji Cornstarch) = 7
A 5/25 mixed solution was used. Comparative Example 1 "Low-density polyethylene" (manufactured by Sumitomo Chemical Co., Ltd.) melted on the base paper described in Example 1 was laminated with a laboratory melt extruder to prepare a substrate for a kraft adhesive tape. Observation of the cross section of this laminated paper with a scanning electron microscope revealed that the thickness of the polyethylene film layer was about 18 microns.
Table 1 shows the test results. Comparative Example 2 The base paper described in Example 1 was used as a base material for a kraft adhesive tape. Table 1 shows the test results. Comparative Example 3 5% polyvinyl alcohol "NH17Q" (degree of polymerization: 1700, degree of saponification: 99 mol%, manufactured by Nippon Synthetic Chemical Industry) was used as a barrier agent on the base paper described in Example 1 at a rate of 5 g / m2 using a Meyer bar. ⁽²⁾ Coating was performed by hand coating, and finished with a super calender at Oken type smoothness of 220 seconds to obtain a base material for a craft adhesive tape. Table 1 shows the test results. COMPARATIVE EXAMPLE 4 12% polyvinyl alcohol "L0302" (polymerization degree: 500, saponification degree: 50 mol%, manufactured by Nippon Synthetic Chemical Industry) was used as a barrier agent on the base paper described in Example 1 at a rate of 5 g / m. ⁽²⁾ Coating was performed by hand coating, and finished with a super calender to Oken type smoothness of 215 seconds to obtain a base material for craft adhesive tape. Table 1 shows the test results. Comparative Example 5 A substrate for a kraft pressure-sensitive adhesive tape was prepared in the same manner as in Example 1, and an evaluation test was performed. However, instead of NL05 of the coating liquid for the barrier layer of Example 1, NL05 / oxidized starch (Oji Ace A, manufactured by Oji Cornstarch) = 50
A / 50 mixed solution was used. Table 1 shows the test results. [Table 1] [Note] * 1 ○: extremely good △: slightly poor ×: extremely poor As can be seen from Table 1, the kraft pressure-sensitive adhesive tape substrates of the examples according to the present invention have satisfactory results. However, the release paper substrate of each comparative example was unsatisfactory in any of the properties of each evaluation item. The substrate for a kraft pressure-sensitive adhesive tape of the present invention comprises:
It has excellent solvent barrier properties comparable to the base material for kraft adhesive tape laminated with polyethylene, and can be easily manufactured with existing paper machines and coating machines, and is extremely excellent in practicality It is.

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Riki Tsukada               1-10-6 Shinonome, Koto-ku, Tokyo Oji               Paper Manufacturing Co., Ltd.                (56) References JP-A-5-269932 (JP, A)

Claims (1)

(57) [Claims] [Claim 1] Kraft expanded paper mainly made of wood pulp and a release agent mainly composed of a water-soluble resin directly formed on one surface of the kraft expanded paper In the base material for a kraft pressure-sensitive adhesive tape having a barrier layer for a solution , the barrier layer containing the water-soluble resin as a main component has a degree of polymerization of 200.
A substrate for a kraft pressure-sensitive adhesive tape, comprising a partially or completely saponified polyvinyl alcohol having a saponification degree of from about 800 to a saponification degree of from 88 to 99.9 mol%.