JP2020158932A - Method for manufacturing base paper for polishing paper - Google Patents

Abstract

To provide base paper for polishing paper excellent in impregnation speed and impregnation amount of an impregnation liquid and having little impregnation unevenness.SOLUTION: A method for manufacturing a base paper for polishing paper of the invention comprises a step of impregnating the base paper with impregnating liquid and then drying it to obtain an impregnated base material, and a step of applying coating liquid for the barrier layer to the impregnated base material, where the liquid surface tension measured by the pendant drop method of the impregnating liquid is 35 to 40 mN/m.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for producing a base paper for abrasive paper, and more particularly to a method for producing a base paper for abrasive paper with less uneven impregnation of an impregnating liquid.

Conventionally, in producing a base paper for polishing paper, a method for producing a base paper for polishing paper has been known in which a base material is impregnated with an impregnating liquid to increase dry strength and wet strength. This type of base paper for abrasive paper is formed by impregnating a base material with an impregnating liquid mainly containing a binder, and is configured so that the impregnating liquid quickly permeates and is retained inside the base material. Various proposals have been made for such base paper for abrasive paper in order to impart the required permeation rate and impregnation rate.

As a technique for improving the impregnation rate and impregnation rate of the impregnation solution, for example, Patent Document 1 has a density of 0.50 g for the purpose of providing an improved base paper for resin impregnation with improved resin impregnation rate and resin impregnation rate. / cm ³ when the formed sheet, made from a raw material pulp showing the light scattering coefficient of 410~580cm ³ / g, characterized by having a density of 0.40～0.60G / cm ^3, a resin-impregnated The base paper is proposed. Further, Patent Document 2 provides an impregnating base paper having a high permeation rate of a resin solution in an impregnation step and a good resin impregnation property in a method for producing an impregnating base paper made from broad-leaved bleached kraft pulp as a raw material. For impregnation, the pulp slurry is centrifugally dehydrated through a wire to remove short fibers to obtain a pulp fiber having a number average fiber length of 0.45 mm or more. A method for producing base paper has been proposed. Patent Document 3 describes SS by removing short fibers in white water when the white water generated in the paper making process is circulated and reused in a method for producing an impregnating base paper made from broad-leaved bleached kraft pulp as a raw material. A method for producing a base paper for impregnation has been proposed, which comprises clarifying the concentration to 200 ppm or less and then circulating and reusing the clarified white water.

Japanese Unexamined Patent Publication No. 01-246499 Japanese Unexamined Patent Publication No. 04-263649 Japanese Unexamined Patent Publication No. 06-033393

As described above, various techniques have been proposed for the base material for impregnation of the base paper for abrasive paper in order to improve the resin impregnation rate and the resin impregnation rate. By the way, in order to use it as abrasive paper, one side is smoothed to make it a sandy surface, while the other side is made rough by increasing the friction, and it is freeness to increase tensile strength and burst strength. However, there is a problem that the air permeability of the impregnating substrate is increased, the resin impregnation rate is lowered, and as a result, the resin impregnation rate is also lowered by performing such a treatment. If the resin impregnation rate decreases for the above reasons, uneven impregnation of the impregnating liquid tends to occur, and if the impregnating liquid contains a colorant, uneven color appears. It is difficult to improve the unevenness only by improving the impregnating base material described in Patent Documents 1 to 3, and further improvement is required.

The present invention has been made in view of such problems, and an object of the present invention is the impregnation rate and the impregnation amount of the impregnating solution (hereinafter, the impregnation rate and the impregnation amount of the impregnating solution are combined to form "impregnation property". It is an object of the present invention to provide a base paper for abrasive paper which is excellent in (expressed as) and has little impregnation unevenness. Since the impregnation rate increases as the impregnation amount increases, the excellent impregnation amount and the excellent impregnation rate have almost the same meaning.

Another object of the present invention is to provide a base paper for polishing paper that satisfies the processing suitability at the time of sanding when processing as polishing paper.

Still other object of the present invention and actions and effects will be easily understood by those skilled in the art by referring to the following description.

The method for producing a base paper for abrasive paper of the present invention is a method for producing a base paper for abrasive paper, which comprises a step of impregnating a base paper with an impregnating liquid and a step of applying a coating liquid for a barrier layer. The liquid surface tension measured by the pendant drop method of is 35 to 40 mN / m.

By such a manufacturing method, since the liquid surface tension of the impregnating liquid is appropriately low, the permeation rate into the substrate becomes high, and when impregnated, the impregnation liquid permeates quickly to prevent uneven impregnation. In particular, color unevenness when impregnated with an impregnating liquid containing a coloring agent such as a coloring pigment is reduced, and it becomes possible to provide a base paper for abrasive paper having an excellent appearance. Further, when the base paper is impregnated with the impregnating liquid and dried, and then the base paper (hereinafter, sometimes referred to as "impregnated base material") is coated with the coating liquid for the barrier layer, the barrier property is high. A barrier layer can be provided. Here, the barrier property is required when applying the adhesive in the sanding process on the abrasive paper base paper, and if the barrier property of the barrier layer is not secured, the adhesive passes through the barrier layer and penetrates into the base material. Problems such as deterioration of appearance and falling of sand after sanding occur.

Further, in a preferred embodiment of the present invention, the impregnating solution may contain a surfactant. The surface tension of the impregnating liquid can be easily controlled.

Further, in a preferred embodiment of the present invention, the surfactant may be a nonionic or anionic surfactant. According to such a configuration, even when a colorant such as a coloring pigment is added to the impregnating liquid, agglomerates are less likely to occur, and a base paper for abrasive paper having an excellent appearance with less mixed foreign matter can be obtained.

Further, in a preferred embodiment of the present invention, the air permeability measured by JIS P 8117: 2009 of the base paper (all "air permeability" described below is measured by this method) is 20 seconds or more. You may. According to such a configuration, it is possible to obtain a base paper for abrasive paper having excellent (high strength) various strengths such as tensile strength.

According to the present invention, it is possible to obtain a base paper for polishing paper that has less uneven impregnation of the impregnating liquid and satisfies the processing suitability at the time of sanding when processing as polishing paper.

It is a chart which shows the structure and evaluation result of each Example and comparative example.

Hereinafter, examples of a method for producing an impregnated paper according to the present invention will be described in detail.

As described above, in the method for producing a base paper for abrasive paper according to the present invention, a coating liquid for a barrier layer is applied to an impregnated base material obtained by impregnating a base paper with an impregnating liquid and then drying the base paper. ..

The base paper of the base paper for abrasive paper used in the present invention contains pulp as a main component. The pulp used here includes unbleached coniferous kraft pulp (NUKP), unbleached coniferous sulphite pulp (NUSP), unbleached broadleaf kraft pulp (LUKP), and unbleached broadleaf sulphite pulp (LUSP). Wood bleached chemical pulp represented by bleached chemical pulp, coniferous bleached kraft pulp (NBKP), coniferous bleached sulphite pulp (NBSP), broadleaf bleached kraft pulp (LBKP), broadleaf bleached sulphite pulp (LBSP), thermomechanical pulp ( TMP), refiner ground pulp (RGP), mechanical pulp typified by crushed wood pulp (GP), semi-chemical pulp with properties between chemical pulp and mechanical pulp, Sansho, ganpaku, bamboo, straw, hemp, bagus, Kenaf , Non-wood pulp such as cotton, synthetic pulp such as SWP (manufactured by Mitsui Kagaku Co., Ltd.), used paper pulp and the like. Among these, it is preferable to use unbleached wood chemical pulp or bleached wood chemical pulp, which has relatively high strength and is inexpensive and easily available.

Further, in the present invention, various chemical fibers can be blended in these pulps in an arbitrary ratio. Examples of such chemical fibers include rayon, recycled fiber typified by cupra, acetate, semi-synthetic fiber typified by triacetate, synthetic fiber typified by acrylic, polyester, nylon and polyurethane, glass fiber, rock fiber, and slug. Examples thereof include fibers, metal fibers, carbon fibers, alumina fibers, ceramic fibers, and inorganic fibers typified by silica fibers. Among these, rayon fiber, polyester fiber, and glass fiber are preferably used because they are easily mixed with pulp to make it easier to increase the bulk and also to improve the dimensional stability. It is possible to blend such various chemical fibers into pulp before and after beating the pulp, but among various chemical fibers, it is preferable to blend the inorganic fibers after beating the pulp. If the inorganic fiber is blended into the pulp before beating, the effect of cutting the fiber to increase the bulk and the effect of dimensional stability are reduced, and there is a risk of causing mechanical loss such as wear of the beating machine blade.

The Canadian standard drainage (freeness) of pulp is preferably in the range of 450-700 ml CSF, more preferably 500-650 ml CSF. If the Canadian standard drainage of pulp is less than 450 ml CSF, the density of the base paper tends to be high, and as a result, the impregnation property of the impregnating liquid may decrease. On the other hand, when the Canadian standard drainage degree of pulp exceeds 700 ml CSF, the entanglement between the fibers is reduced, so that the tensile strength and the burst strength are likely to decrease, and the fibers may fall off from the base paper. If the fibers fall off from the impregnation base material, the surrounding environment is deteriorated in the papermaking process, impregnation, coating, and other processing processes, and foreign matter is mixed into the product, which is not preferable. The method of beating the pulp is not particularly limited, and any beating machine such as beater, Jordan, deluxe finer, double disc refiner, etc. may be used alone or in combination.

The base paper used in the present invention can be obtained by making paper using a pulp slurry. The pulp slurry contains various paper-making materials such as sulfuric acid bands, fillers, sizing agents, paper strength agents, yield improving agents, coloring dyes, coloring pigments, and bulking agents, as long as the effects intended by the present invention are not impaired. Can be made to. As the filler, one or more known fillers such as hydrated silicic acid, white carbon, talc, kaolin, clay, calcium carbonate, titanium oxide, aluminosilicate, calcined clay, barium sulfate, and synthetic resin filler can be used. ..

When using a sizing agent for the base paper, a paraffin wax sizing agent, a microcrystalline wax sizing agent, a carnauba (carnauba wax) sizing agent, an alkyl keten dimer wax sizing agent, a rosin sizing agent, an alkenyl anhydride succinic acid One or more of sizing agents, styrene acrylic sizing agents, and the like can be used. However, since the impregnating base material of the present invention is used for impregnating an aqueous impregnating liquid, it is preferable to use a sizing agent in a very small amount or not to use a sizing agent. Excessive use of sizing agents is not preferred as it inhibits the penetration of the impregnating solution.

When a paper strength agent is used for the base paper, starch, cationized starch, other modified starch, polyacrylamide resin, urea formalin resin, melamine formalin resin, plant gum, polyvinyl alcohol, modified polyvinyl alcohol, rubber latex , Polyvinyl oxide, polyamide resin, etc. that promote the improvement of dry paper strength, urea formaldehyde resin, melamine formaldehyde resin, polyamide epichlorohydrin-based epoxy resin, etc. that promote the improvement of wet paper strength, etc. be able to. Paper strength agents are effective in improving tensile strength and burst strength, but if the amount added is too large, the density of the base paper may increase and the impregnation property may decrease. In the present invention, when the paper strength agent is added to the pulp slurry, the amount added is preferably in the range of 0.05 to 5% by mass, more preferably 0.1 to 4% by mass, based on the total amount of pulp. It is in the range, more preferably in the range of 0.2 to 2% by mass. If the amount of the paper strength agent added exceeds 5% by mass, the density of the base paper becomes high and the excess paper strength enhancer itself enters the gaps between the fibers to reduce the gaps, which may impair the impregnation property of the impregnating liquid. is there. Further, if the amount of the paper strength enhancer that cannot be fixed to the pulp fiber increases, the trouble that the paper strength enhancer pollutes the process also leads.

In the present invention, the method for making the base paper is not particularly limited, and a conventionally well-known paper machine such as a circular net paper machine, a short net paper machine, a long net paper machine, and a combination paper machine of these paper machines is used. Can be made by single layer or papermaking. In the case of abstracting, a paper strength agent such as starch for interlayer coating may be spray-coated to prevent delamination of each layer of abstracting. The drying method of the paper making machine is not particularly limited, and a multi-cylinder cylinder dryer method, a yanky dryer method, an air drying method typified by hot air drying, a radiant drying method typified by an infrared device, and the like can be used. Among these, the multi-cylinder cylinder dryer method or the Yankee dryer method is preferable, and the Yankee dryer method is particularly preferable. By drying with the Yankee dryer method, the mirror surface of the Yankee dryer is transferred to one side of the base paper to form a single-gloss paper, so that one side of the base paper can be a highly smooth surface suitable for sanding. At the same time, the other surface can be a surface with reduced slippage when used as abrasive paper.

In the present invention, the base paper is made and then impregnated with the impregnating liquid to obtain an impregnated base material. The impregnating solution is prepared by mixing water and a polymer resin. Examples of the polymer resin used here include oxidized starch, phosphate esterified starch, cationized starch, starch-based typified by other modified starches, styrene-butadiene latex (SBR), acrylonitrile-butadiene latex (NBR), and natural rubber. Butadiene latex represented by latex (NR), acrylic latex, urethane resin, polyvinyl acetate (PVAC), vinyl acetate represented by ethylene vinyl acetate (EVA), natural rubber, various gums, casein, polyvinyl alcohol One or more kinds of materials such as (PVA) that contribute to the improvement of the paper strength of the base paper can be used. Among these, styrene-butadiene latex (SBR), which is relatively inexpensive and easily increases the strength of dry paper and the strength of wet paper, is preferable.

Here, the impregnating liquid includes a viscosity regulator, a sizing agent, a paper strength agent, a moisturizer, a water repellent, a pH adjuster, a wetting agent, a film forming aid, a cross-linking agent, a coloring agent, etc., depending on the required functions. Various auxiliary agents may be added. As the colorant, both a color pigment and a color dye can be used, but it is preferable to use a color pigment that causes less discoloration when rubbed, especially when rubbed with water.

In the present invention, the impregnating liquid is adjusted so that the liquid surface tension measured by the pendant drop method is 35 to 40 mN / m. By setting the liquid surface tension in such a range, the permeation rate of the impregnating liquid into the base material can be set in an appropriate range, and impregnation unevenness is less likely to occur. In particular, color unevenness when impregnated with an impregnating solution containing a coloring agent such as a coloring pigment is reduced. When the liquid surface tension is less than 35 mN / m, the impregnation unevenness of the impregnating liquid is reduced, but there arises a problem that the barrier property after impregnation cannot be ensured. On the contrary, when the liquid surface tension exceeds 40 mN / m, the impregnation unevenness of the impregnating liquid becomes large.

In order to evenly impregnate the base paper with the impregnating liquid, it is advantageous that the base paper has a small air permeability, but such a base paper has a problem that the tensile strength and the burst strength are also small. However, according to the findings of the present inventors, by adjusting the surface tension of the impregnating liquid so as to be within the above range, uneven impregnation of the impregnating liquid is less likely to occur even if the air permeability of the base paper is relatively high. Can be done. By setting the surface tension of the impregnating liquid within the above range, even if the air permeability of the base paper is 20 seconds or more, the impregnation unevenness of the impregnating liquid is small, and the base paper for abrasive paper having relatively high tensile strength and burst strength can be obtained. It becomes possible to obtain. The upper limit of the air permeability of the base paper is not particularly limited, but 200 seconds or less is preferable, 80 seconds or less is more preferable, and 50 seconds or less is the most preferable as a range in which the impregnation speed of the impregnating liquid is not extremely lowered. preferable.

In the present invention, the method for controlling the liquid surface tension of the impregnating liquid is not particularly limited, but in order to increase the liquid surface tension, for example, a material such as a binder that does not contain a surfactant in advance may be selected. There is a way to do it. On the contrary, the method of adding a surfactant is relatively easy to reduce the liquid surface tension. Since the liquid surface tension (20 ° C.) of pure water is approximately 72 mN / m, the liquid surface tension of the impregnated liquid is reduced by adding a material such as a binder or a surfactant to water. Become.

The surfactant used in the impregnating solution is not particularly limited, and general surfactants described on the website of the Japan Surfactant Industry Association can be used, but they must be nonionic or anionic surfactants. Is preferable. By using a nonionic or anionic surfactant, it becomes difficult to form a complex even when a coloring pigment that is mainly anionic is added to the impregnating solution, and agglomerates are less likely to be generated in the impregnating solution. There is little mixing, and it is unlikely to cause color unevenness after impregnation with the impregnating solution.

Specifically, examples of the anionic surfactant include carboxylates such as alkyl ether carboxylates, linear alkylbenzene sulfonates (LAS), α-sulfo fatty acid methyl ester salts (MES), and α-olefin sulfonates. Sulfonates such as (AOS), alkyl sulfates (AS), sulfates such as polyoxyethylene alkyl sulfates (AES), phosphates such as higher alcohols and their ethylene oxide adducts, acyl-. Examples thereof include amino acid type activators such as N-methyltaurine salt. As nonionic surfactants, ester types such as glycerin fatty acid ester, sorbitan fatty acid ester, and sucrose fatty acid ester, polyoxyethylene (POE) alkyl ether, polyoxyethylene (POE) alkylphenyl ether, and polyoxyethylene polyoxypropylene. Surfactants of ether type such as glycol, ester ether type such as fatty acid polyethylene glycol and fatty acid polyoxyethylene sorbitan, and alkanolamide type such as fatty acid alkanolamide, and the like can be mentioned.

The amount of impregnated liquid impregnated into the base paper varies depending on the required strength of the base paper for abrasive paper, paper density, paper thickness, etc., but the solid content is 10 to 80% of the weight of the paper after impregnation and drying. It is preferable to have. If the impregnation amount is 10% or less, the strengths of the base paper for abrasive paper are insufficient, and if the impregnation amount is 80% or more, the improvement of the strengths reaches a plateau, which is economically disadvantageous.

The impregnation method of the impregnating liquid is not particularly limited, and may be a method of impregnating the base paper in a series of steps with the papermaking step, or a method of impregnating the base paper in another step after making the paper. Further, the impregnation method is not particularly limited, and a known impregnation method can be used. For example, impregnation can be performed by various known impregnation methods such as a size press method, a dipping method, a coater method, and a spray method. Among these, the dipping method is preferable because the impregnating liquid can easily penetrate into the inside of the base paper.

The drying method of the base paper after impregnating the base paper with the impregnating liquid is not particularly limited, and an air drying method typified by hot air drying such as a multi-cylinder cylinder dryer method, a Yankee dryer method, and an air dryer method. A radiant drying method typified by an infrared device can be used. Of these, the hot air drying method is preferable. Since the impregnated paper coated with the impregnating liquid can be floated with hot air and dried, the equipment such as rolls can be dried without being soiled with the impregnating liquid.

After impregnating the base paper with the impregnating liquid and drying it, the coating liquid for the barrier layer is applied and dried, and the barrier layer is provided on the surface of the base paper for polishing paper. The base paper for abrasive paper of the present invention is obtained by applying an adhesive to the surface of the barrier layer, sanding the surface of the barrier layer to adhere abrasive particles, and processing the barrier layer into abrasive paper. It is provided to prevent excessive penetration of the adhesive into the base paper for abrasive paper at the time of attachment. If the barrier layer is not provided, the adhesive will permeate too much into the base paper for abrasive paper during sanding, and as a result, the adhesiveness of the abrasive particles to the base paper for abrasive paper will be impaired, and the abrasive particles will fall off due to sand falling. , There is a risk that it will be defective as abrasive paper.

The coating liquid for the barrier layer in the present invention is prepared by mixing water and a polymer resin. Here, as the polymer resin, for example, styrene-butadiene latex (SBR), acrylonitrile-butadiene latex (NBR), butadiene-based latex typified by natural rubber latex (NR), acrylic latex, urethane resin, polyvinyl acetate ( One or more kinds of vinyl acetate type represented by PVAc), ethylene vinyl acetate (EVA), natural rubber, various gums, casein, polyvinyl alcohol (PVA) and the like can be used. Among these, styrene-butadiene latex (SBR), which has easy barrier performance and is relatively inexpensive, is preferable. The coating liquid for the barrier layer further requires a viscosity adjuster, a sizing agent, a paper strength agent, a moisturizer, a water repellent, a pH adjuster, a wetting agent, a film forming aid, a cross-linking agent, etc. May be added.

The amount of the coating liquid for the barrier layer is preferably 8 to ²⁰ g / m ^{2 in} terms of solid content per one side of the base paper, and more preferably 10 to 17 g / m ² . If the coating amount is less than 8 g / m ^2, the adhesive at the time of sanding may permeate too much into the base paper for abrasive paper. On the contrary, if it exceeds 20 g / m ² , the barrier layer becomes hard and problems such as cracking are likely to occur, and it is economically disadvantageous.

In the present invention, the base paper is impregnated with the impregnating liquid, dried, and then coated with the coating liquid for the barrier layer. The coating of the coating liquid for the barrier layer is a series of steps including the impregnation liquid impregnation step. Alternatively, it may be a separate process. The method of applying the barrier layer coating liquid to the base paper after impregnation is not particularly limited, and the coating can be applied by various known coating methods such as a coater method and a spray method. For example, blade coater, roll coater, reverse roll coater, air knife coater, die coater, bar coater, gravure coater, curtain coater, champ flex coater, lip coater, rod coater, gate roll coater, spray coater, size press coater, film transfer. The barrier layer of the present invention can be obtained by coating with an off-machine coater or an on-machine coater depending on a coating method such as a mold coater.

The drying method after coating with the coating liquid for the barrier layer is not particularly limited, and is represented by a multi-cylinder cylinder dryer method, a yankee dryer method, an air drying method typified by hot air drying such as an air dryer, and an infrared device. A radiation drying method or the like can be used. Among these, the hot air drying method is preferable because the coated paper coated with the coating liquid for the barrier layer can be floated with hot air and dried, so that the equipment such as rolls can be dried without being soiled with a binder.

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these examples. In addition, "parts" and "%" in the example indicate mass parts or mass% in terms of solid content, respectively, unless otherwise specified. For the sulfate band, the number of solids as aluminum sulfate hexahydrate is shown.

[Base paper A]
32 parts of NUKP having a pre-beating freeness of 760 ml CSF, 37 parts of NBKP having a pre-beating freeness of 750 ml CSF and 31 parts of LBKP having a pre-beating freeness of 636 ml CSF were mixed and beaten, and dispersed in water to obtain a pulp slurry having a freeness of 550 ml CSF. To 100 parts of the pulp slurry, 2.5 parts of a sulfuric acid band (manufactured by Techno Hokuetsu Co., Ltd.) and 0.35 parts of an epoxy-modified polyamide (trade name: Hermide PY-525A, manufactured by Harima Kasei Co., Ltd.) were added to obtain a paper material. After that, a piece of paper with a basis weight of 90 g / m ² , a density of 0.70 g / cm ³ , and an air permeability of 29.8 seconds / 100 cc is made by making a two-layer paper using the paper material and drying it with a Yankee dryer. A glossy base paper A was obtained.

[Base paper B]
32 parts of NUKP having a pre-beating freeness of 760 ml CSF, 37 parts of NBKP having a pre-beating freeness of 750 ml CSF, and 31 parts of LBKP having a pre-beating freeness of 636 ml CSF were mixed and beaten, and dispersed in water to obtain a pulp slurry having a freeness of 580 ml CSF. To 100 parts of the pulp slurry, 2.5 parts of a sulfuric acid band (manufactured by Techno Hokuetsu Co., Ltd.) and 0.35 parts of an epoxy-modified polyamide (trade name: Hermide PY-525A, manufactured by Harima Kasei Co., Ltd.) were added to obtain a paper material. After that, a piece of paper with a basis weight of 90 g / m ² , a density of 0.68 g / cm ³ , and an air permeability of 18.2 seconds / 100 cc is made by making a two-layer paper using the paper material and drying it with a Yankee dryer. A glossy base paper B was obtained.

[Base paper C]
32 parts of NUKP having a pre-beating freeness of 760 ml CSF, 37 parts of NBKP having a pre-beating freeness of 750 ml CSF and 31 parts of LBKP having a pre-beating freeness of 636 ml CSF were mixed and beaten, and dispersed in water to obtain a pulp slurry having a freeness of 550 ml CSF. To 100 parts of the pulp slurry, 2.5 parts of a sulfuric acid band (manufactured by Techno Hokuetsu Co., Ltd.) and 0.35 parts of an epoxy-modified polyamide (trade name: Hermide PY-525A, manufactured by Harima Kasei Co., Ltd.) were added to obtain a paper material. After that, the paper was made by two-layer papermaking using the paper material and dried with a multi-cylinder cylinder dryer. The basis weight was 104 g / m ² , the density was 0.59 g / cm ³ , and the air permeability was 28.0 seconds / 100 cc. A base paper C having no gloss on both sides was obtained.

[Pre-preparation impregnating solution D]
10.5 parts of styrene butadiene latex (trade name: LACSTAR 7310K, manufactured by DIC, 49% by mass), 0.13 parts of black pigment (trade name: Sundai DP Black CN / manufactured by Sanyo Dye) as a colorant, blue pigment (Product name: SP Blue HB / Mikuni Color) 0.03 part was dispersed in water to obtain an impregnating solution D.

[Coating liquid E for barrier layer]
Styrene-butadiene latex (trade name: L-1638, manufactured by Asahi Kasei Corporation, 48% by mass) was diluted with water to 40% by mass to obtain a coating liquid E for a barrier layer.

(Example 1)
Anionic surfactant (trade name: TAYCA Lite N4133, TAYCA component concentration 35%) was added to the pre-preparation impregnating solution D so that the component concentration of the surfactant in the impregnating solution was 0.245%. It was used as an impregnating solution. The surface tension of the impregnated liquid measured by the pendant drop method was 35.5 mN / m. After dipping the base paper A into the obtained impregnating liquid, excess impregnating liquid was removed with a squeeze roll, and then dried with an air dryer to obtain an impregnated base material. The impregnation amount of the impregnating liquid (the amount as the impregnating liquid instead of the solid content, the same applies to the following Examples and Comparative Examples) was 93 g / m ² . Next, the barrier layer coating liquid E was applied to one surface of the impregnated base material with an air knife coater so as to have a solid content of 12 g / m ^2, and dried with an air dryer to obtain a base paper for abrasive paper. It was.

(Example 2)
In Example 1, an anionic surfactant (trade name: TAYCA Lite N4133, TAYCA component concentration 35%) was added and impregnated so that the component concentration of the surfactant in the impregnating solution was 0.105%. A base paper for abrasive paper was obtained in the same manner as in Example 1 except that the liquid was used. The liquid surface tension of the impregnating liquid measured by the pendant drop method was 38.4 mN / m, and the impregnated amount of the impregnating liquid was 90 g / m ² .

(Example 3)
In Example 1, instead of the anionic surfactant (trade name: TAYCA Lite N4133, component concentration 35% manufactured by TAYCA), a nonionic surfactant (trade name: Neugen ET-116, component manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) A base paper for polishing paper was obtained in the same manner as in Example 1 except that (concentration 100%) was added so that the component concentration of the surfactant in the impregnating solution was 0.3% to obtain an impregnating solution. The liquid surface tension of the impregnating liquid measured by the pendant drop method was 36.3 mN / m, and the impregnated amount of the impregnating liquid was 92 g / m ² .

(Example 4)
In Example 2, a base paper for polishing paper was obtained in the same manner as in Example 2 except that base paper B was used instead of base paper A. The impregnation amount of the impregnating liquid was 95 g / m ² .

(Example 5)

A base paper for abrasive paper was obtained in the same manner as in Example 1 except that the base paper C was used instead of the base paper A in the first embodiment. The impregnation amount of the impregnating liquid was 93 g / m ² .

(Comparative Example 1)
In Example 1, an anionic surfactant (trade name: TAYCA Lite N4133, TAYCA component concentration 35%) was added and impregnated so that the component concentration of the surfactant in the impregnating solution was 0.35%. A base paper for abrasive paper was obtained in the same manner as in Example 1 except that the liquid was used. The liquid surface tension of the impregnating liquid measured by the pendant drop method was 34.4 mN / m, and the impregnation amount of the impregnating liquid was 95 g / m ² .

(Comparative Example 2)
In Example 3, a nonionic surfactant (trade name: Neugen ET-116, 100% component concentration manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) was added so that the component concentration of the surfactant in the impregnating solution was 1.0%. A base paper for abrasive paper was obtained in the same manner as in Example 3 except for the above. The liquid surface tension of the impregnating liquid measured by the pendant drop method was 34.0 mN / m, and the impregnated amount of the impregnating liquid was 96 g / m ² .

(Comparative Example 3)
In Example 1, a base paper for abrasive paper was obtained in the same manner as in Example 1 except that an impregnating liquid was obtained without adding a surfactant. The liquid surface tension of the impregnating liquid measured by the pendant drop method was 49.7 mN / m, and the impregnated amount of the impregnating liquid was 80 g / m ² .

(Comparative Example 4)
In Example 4, a base paper for abrasive paper was obtained in the same manner as in Example 4 except that an impregnating liquid was obtained without adding a surfactant. The liquid surface tension of the impregnating liquid measured by the pendant drop method was 49.7 mN / m, and the impregnated amount of the impregnating liquid was 85 g / m ² .

(Comparative Example 5)
In Example 5, a base paper for abrasive paper was obtained in the same manner as in Example 5 except that an impregnating liquid was obtained without adding a surfactant. The liquid surface tension of the impregnating liquid measured by the pendant drop method was 49.7 mN / m, and the impregnating amount of the impregnating liquid was 90 g / m ² .

(Comparative Example 6)
In Example 1, an anionic surfactant (trade name: TAYCA Lite N4133, TAYCA component concentration 35%) was added and impregnated so that the component concentration of the surfactant in the impregnating solution was 0.035%. A base paper for abrasive paper was obtained in the same manner as in Example 1 except that the liquid was used. The liquid surface tension of the impregnating liquid measured by the pendant drop method was 41.0 mN / m, and the impregnated amount of the impregnating liquid was 86 g / m ² .

FIG. 1 shows the contents of the surfactant in each Example and Comparative Example, the liquid surface tension of the impregnating liquid using the surfactant, the impregnating base material used, and the evaluation results of the obtained impregnated paper. In addition, each evaluation was performed by the following method.

<Liquid surface tension of impregnating liquid>
The surface tension of the impregnating solution was measured by the pendant drop method using a dynamic contact angle meter FIBRO DAT1100 MkII (manufactured by FIBRO system ab). The indoor environment at the time of measurement was 23 ± 1 ° C. and 50 ± 2% RH, and the temperature of the impregnating solution was 23 ° C. The size of the droplet was automatically set in the case of the device, but was 4 to 10 ml, and the measurement was performed immediately after the formation of the droplet.

<Air permeability of base paper>
The air permeability of the paper was measured according to JIS P 8117: 2009 (paper and paperboard? Air permeability and air permeability resistance test method (intermediate region) -Garley method).

<Uneven impregnation>
The color unevenness of the impregnated paper coated with the impregnating liquid on the impregnating base material was visually observed and evaluated in four stages.
⊚: There is almost no color unevenness. Passed.
◯: Color unevenness is seen weakly. Passed.
Δ: Color unevenness is seen quite strongly. failure.
X: Color unevenness is very strong. failure.

<Barrier performance>
Brilliant Green (manufactured by Wako Pure Chemical Industries, Ltd.) is added to ethanol (manufactured by Wako Pure Chemical Industries, Ltd.) in an amount of 1% by mass based on ethanol and mixed to prepare an evaluation solution. The evaluation liquid is applied to the surface of the barrier layer of the base paper for abrasive paper with absorbent cotton in a width of 2 cm and a length of 15 cm, and after 10 seconds, the liquid adhering to the filter paper is wiped off. Pinholes that exceeded the barrier layer and were absorbed by the paper substrate and became darker in color were observed and evaluated on a 4-point scale.
⊚: There is no pinhole. Passed.
◯: There are 3 or less pinholes. Passed.
Δ: 3 to 9 pinholes. failure.
X: 10 or more pinholes. failure.

As is clear from FIG. 1, the impregnated papers obtained in Examples 1 to 5 using the impregnated liquid having a liquid surface tension of 35 to 40 mN / m have almost no or weak impregnation unevenness. The barrier performance was also good.

On the other hand, the base papers for abrasive paper obtained in Comparative Example 1 and Comparative Example 2 using the impregnating liquid having a liquid surface tension of less than 35 mN / m are inferior in barrier performance, and the adhesive at the time of sanding is for abrasive paper. There is a risk that it will penetrate too much into the base paper. In addition, the base papers for abrasive paper obtained in Comparative Examples 3 to 6 using an impregnating liquid having a liquid surface tension of more than 40 mN / m were inferior in impregnation unevenness.

Claims (4)

A method for producing a base paper for abrasive paper, which comprises a step of impregnating a base paper with an impregnating liquid and then drying it to obtain an impregnated base paper, and a step of applying a coating liquid for a barrier layer to the impregnated base paper.
A method for producing a base paper for abrasive paper, wherein the liquid surface tension measured by the pendant drop method of the impregnating liquid is 35 to 40 mN / m. The method for producing a base paper for abrasive paper according to claim 1, wherein the impregnating liquid contains a surfactant. The method for producing a base paper for abrasive paper according to claim 2, wherein the surfactant is a nonionic or anionic surfactant. The method for producing a base paper for abrasive paper according to any one of claims 1 to 3, wherein the air permeability of the base paper measured according to JIS P 8117: 2009 is 20 seconds or more.

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