JP2009167535A - Base paper for support and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide base paper for supports, excellent in a sizing property and little in foreign matter defects, and to provide a method for producing the same. <P>SOLUTION: Provided is the base paper for the supports, used for the supports for image materials prepared by coating both the sides of a paper substrate with a polyolefin resin. In the base paper, a pulp slurry used for the raw paper contains an inorganic pitch control agent as a pitch control agent in an amount of 0.01-1 mass% per 100 mass% of the pulp, at least an alkylketene dimer as an inner sizing agent in an amount of 0.1-1 mass% per 100 mass% of the pulp, and further an inorganic pH adjusting agent as a pH-adjusting agent in an amount of 0.05 mass% or more, and has a pH of 7.5 or more, when making paper. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a base paper for a support used for a support for an image material in which both sides of a paper substrate are coated with a polyolefin resin, and a method for producing the same. More specifically, the present invention is excellent in sizing properties and has few foreign matter defects. The present invention relates to a support base paper and a method for producing the same.

  Conventionally, in the case of a support for image material, it is known to add a sizing agent to pulp fiber slurry in order to prevent the developer from entering from the edge of the photographic paper during development. It is described that an alkyl ketene dimer is often used as a typical sizing agent at that time (for example, see Patent Documents 1 and 2).

  Further, the level of defects (number of defects / area) mixed in the base paper of the image material support is required to be extremely small compared to general high-quality paper. In recent years, for the purpose of reducing energy, the paper industry tends to reduce the amount of water used during paper manufacture, and the support also tends to reduce the amount of water used during base paper manufacture. If the amount of water used during paper manufacture is reduced, the chemicals introduced into the system will continue to circulate or the water temperature in the system will become high. As a result, many defects derived from the chemicals introduced when the support is produced occur. Then, although the method of raising the yield of a chemical | medical agent is proposed, it has not resulted in sufficient improvement (for example, refer patent documents 3-4).

Moreover, in order to prevent pitch, the method of adding talc as an inorganic pitch control agent is known. In systems using MP (mechanical pulp) or DIP (deinked pulp), pitch is prevented by adding 0.8 to 2.6 wt% (maximum) of talc to 100 wt% of pulp. Is written, but there is no description regarding the defect of foreign matters (for example, see Non-Patent Document 1).
JP 63-180948 A Japanese Patent Laid-Open No. 3-62028 Japanese Patent Laid-Open No. 4-281095 Japanese Patent No. 3092694 Papa Gikyo Magazine Vol.59, No.10

  An object of the present invention is to provide a base paper for a support which is excellent in size and has few foreign substance defects, and a method for producing the same.

The above object of the present invention has been achieved by the following invention.
1) In a base paper for a support used for a support for an image material in which both surfaces of a paper substrate are coated with a polyolefin resin, an inorganic pitch control agent is used as a pitch control agent in the pulp slurry used for the base paper. 0.01 to 1% by mass, 0.1 to 1% by mass of an alkyl ketene dimer as an internal sizing agent, 0.05% by mass or more of an inorganic pH adjuster as a pH adjuster, and pulp slurry during paper making The base paper for support is characterized by having a pH of 7.5 or more.

  2) The base paper for a support according to 1), wherein the inorganic pH adjuster is calcium carbonate.

  3) The base paper for a support according to 1) or 2), wherein the internally added sizing agent is an anionic alkyl ketene dimer.

  4) In a base paper for a support used for a support for an image material in which both surfaces of a paper substrate are coated with a polyolefin resin, an inorganic pitch control agent is added as a pitch control agent to the pulp slurry used for the base paper. 0.01 to 1% by mass, 0.1 to 1% by mass of an alkyl ketene dimer as an internal sizing agent, 0.05% by mass or more of an inorganic pH adjuster as a pH adjuster, and the pulp slurry during papermaking A method for producing a base paper for a support, wherein the paper is made with a pH of 7.5 or more.

  According to the present invention, it is possible to provide a base paper for a support that is excellent in size and has few foreign substance defects, and a method for producing the same.

Hereinafter, the base paper for an image material support of the present invention and the production method thereof will be described in detail.
First, the base paper for image material support in the present invention will be described. The present inventor first produces a base paper of the support at a high temperature (at least a papermaking system, particularly a temperature per head box of 45 ° C. or more) using an alkyl ketene dimer (hereinafter referred to as AKD) as a sizing agent. The foreign matter defects were investigated. As a result, it has been found that there are many cases where a large amount of AKD is contained in the foreign substance defect and a talc component is contained.

Therefore, when the origin of talc was investigated, it was found that it was a pitch control agent added to the cooking / bleaching process during pulp production. The pitch control agent is originally added in order to eliminate foreign matter defects derived from the resin component in the pulp by adsorbing the resin component in the pulp manufacturing process and discharging it together with the pulp outside the pulp manufacturing process. .
As a result, a normal pulp contains a pitch control agent although there is a difference in amount.
In general, pitch control agents often use inorganic particles having a large specific surface area.

In general paper such as high-quality paper used for writing or offset printing, high sizing properties are not required. Therefore, the amount of the sizing agent added to the pulp slurry in the papermaking process is also the support of the present invention. Compared to the production of the base paper, there are few occurrences of foreign material defects derived from the sizing agent. However, when the base paper of the support is finally used as a photographic printing paper, it requires a high sizing property in order to prevent the developer from penetrating into the base paper in the development process. As for the addition amount of AKD, it is necessary to add 0.1 mass% or more with respect to a pulp. The amount of sizing agent added is larger than that in the case of producing general printing paper, and when producing the base paper of the support that is required to have a very small number of foreign substance defects mixed in the base paper, the quality of the pulp, It has been found that it is necessary to pay attention to the pH adjustment method during papermaking.
First, the pulp quality to be noted in the present invention is the amount of the inorganic pitch control agent contained in the pulp. The inorganic pitch control agent contained in the pulp easily adsorbs a small emulsion in the slurry, and the inorganic pitch control agent and the sizing agent are aggregated depending on the conditions in the slurry, and foreign matter defects are likely to occur. And in order to suppress generation | occurrence | production of a foreign material defect, it discovered that it was necessary to adjust the quantity of the inorganic type pitch control agent contained in a pulp so that it might become 0.01-1 mass% with respect to a pulp. It was.

  When the amount of the inorganic pitch control agent to be added is less than 0.01% by mass with respect to the pulp, the pitch trouble prevention effect due to the combination of the resin acid present in the pulp and the inorganic pitch control agent is not sufficient, Also, when added in excess of 1% by weight with respect to the pulp, the pitch trouble prevention effect is excellent, but the agglomeration between the inorganic pitch control agent and the sizing agent becomes severe, and the foreign matter defects increase. Can not do it.

  Next, the present inventor has found that the degree of aggregation between the pulp containing the inorganic pitch control agent as described above and AKD varies depending on the pH of the slurry and the pH adjusting method. The pH in the slurry is adjusted by the pH of the pulp itself and the chemicals to be added. It was found that when the pH of the slurry was 7.5 or less, the interaction between the inorganic pitch control agent in the pulp and AKD was strengthened, and foreign matter defects were likely to occur. And in order to suppress generation | occurrence | production of a foreign material defect, it discovered that it was necessary to add 0.05 mass% or more of inorganic type pH adjusters in a pulp. By adding 0.05% by mass or more of an inorganic pH adjuster to the pulp, it is possible to control the pH of the pulp and maintain the pH at 7.5 or more. Moreover, it is not preferable to raise the pH of the pulp too much from the viewpoint of size. For this reason, it is preferable to add 0.05 to 5 mass%, and it is particularly preferable to add 0.05 to 3 mass% as the amount of the inorganic pH adjusting agent added to the pulp. Further, the pH of the pulp slurry in the present invention is a pH measured at a pulp slurry temperature of 42 ± 3 ° C.

  Examples of the inorganic pitch control agent used in the present invention include porous inorganic substances such as talc and clay, and it is particularly preferable to use talc because the adsorption effect of the resin acid present in the pulp is large. On the other hand, the organic pitch control agent is insufficient in the adsorption effect of the resin acid present in the pulp, so the organic acid alone cannot be used in the present invention, but the adsorption effect of the resin acid present in the pulp is impaired. You may use together with an inorganic type pitch control agent in the range which is not.

  Next, the pH adjustment method was examined. In the present invention, adjusting the pH with a water-soluble alkaline metal salt or the like is more likely to cause a foreign matter defect than adjusting the pH with an insoluble alkaline metal salt, and the monovalent alkaline metal It has been found that the use of a salt is more likely to cause foreign matter defects than the use of a divalent alkaline metal salt.

  Examples of the insoluble alkaline metal salt in the present invention include, for example, calcium carbonate, magnesium hydroxide, magnesium oxide, and the like. Particularly preferred is the use of calcium carbonate because foreign matter defects are reduced.

  The pulp constituting the base paper for support of the present invention is usually LBKP (hardwood bleached kraft pulp), NBKP (softwood bleached kraft pulp), LBSP (hardwood bleached sulfite pulp), NBSP (softwood bleached sulfite) used for papermaking. Conventionally known chemical pulps such as pulp) can be used, and various mechanical pulps such as GP (ground pulp) and TMP (thermomechanical pulp), waste paper pulp, non-wood pulp, synthetic pulp, various types Pulp obtained by subjecting pulp fibers to chemical treatment such as mercerization can be used alone or in combination as long as the quality of the base paper is not impaired.

  As the AKD used as the internal sizing agent in the present invention, it is preferable to use an anionic AKD that can suppress aggregation of the inorganic pitch control agent and AKD and suppress foreign matter defects. Moreover, the amount of AKD to be added needs to be 0.1 to 1% by mass with respect to the pulp. When the addition amount of AKD is less than 0.1% by mass with respect to the pulp, the expression of size becomes insufficient, and when the addition amount exceeds 1% by mass with respect to the pulp, the addition amount of AKD The effect of improving the expression of size on the surface becomes small, and it becomes a cause of various stains during actual operation, so it cannot be used. Preferably, it is preferable to add 0.2 to 0.5% by mass with respect to the pulp from the effect of expressing the size and the balance of dirt during actual operation.

  In the pulp slurry used in the present invention, various commonly known papermaking aids can be used. For example, calcium carbonate, magnesium carbonate, kaolin, delaminated kaolin, calcined kaolin, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, aluminum silicate, diatomaceous earth, silicic acid White inorganic pigments such as calcium, synthetic amorphous silica, colloidal silica, cation-modified colloidal silica, aluminum hydroxide, alumina, alumina hydrate, lithopone, zeolite, hydrohalosite, magnesium hydroxide, organic pigment, paper strength Starch, polyacrylamide resin, polyvinyl alcohol, galactomannan as agent, polyamide polyamine epichlorohydrin resin as wet paper strength agent, water-soluble aluminum salt such as aluminum chloride, sulfate band as fixing agent However, it is advantageous to contain a suitable combination of alkenyl or alkyl succinic anhydride, fatty acid metal salt, fatty acid, epoxy-based higher fatty acid amide, etc., as well as a yield improver, dye, pigment, fluorescent whitening agent, etc. as an internal sizing agent. It is.

  The paper machine used in the production of the support base paper of the present invention is not particularly limited as long as it is a general paper machine, and is a long net paper machine, a twin wire paper machine, a hybrid paper machine, a circular net paper machine, a Yankee paper machine. A paper machine known in the paper industry such as a machine and various combination paper machines can be used as appropriate.

  The base paper for support of the present invention can be tab-sized or size-pressed with a liquid containing various additives including a water-soluble polymer additive. Examples of the water-soluble polymer additive used in the present invention include starch, cationized starch, polyvinyl alcohol, carboxy-modified polyvinyl alcohol, carboxymethyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, cellulose sulfate, gelatin, casein, and polyacrylic acid. Sodium, styrene-maleic anhydride copolymer sodium salt, sodium polystyrene sulfonate, etc. are used. Further, petroleum resin emulsion, ammonium salt of styrene-maleic anhydride copolymer alkyl ester, alkyl ketene dimer emulsion as sizing agent Latex or emulsion such as styrene-butadiene copolymer, ethylene-vinyl acetate copolymer, polyethylene, vinylidene chloride copolymer, etc. Sodium chloride, calcium chloride, sodium hydroxide, etc. as inorganic agents, glycerin, polyethylene glycol, etc. as hygroscopic substances, clay, kaolin, talc, barium sulfate, titanium oxide, etc. as pigments, hydrochloric acid, sulfuric acid as pH adjusters Caustic soda, sodium carbonate, etc. are used, and other additives such as dyes, coloring pigments, and optical brighteners can also be used in combination.

  The polyolefin resin used for coating both sides of the base paper for support is selected from α-olefin homopolymers such as polyethylene and polypropylene, α-olefin copolymers, and mixtures of these various polymers. Can do. Particularly preferred polyolefin resins are low density polyethylene and a mixture thereof mainly composed of low density polyethylene. Although there is no restriction | limiting in particular in the molecular weight of polyolefin resin, Usually, it may be in the range of 20,000-200,000. There is no restriction | limiting in particular about the thickness of a polyolefin resin coating layer, It can determine according to the thickness of the resin layer of the support body for the conventional image material. The thickness is usually selected from the range of 10 to 100 μm, and in particular from 15 to 50 μm. The polyolefin resin coating layer that forms the surface on which the photographic emulsion is coated can be mixed with commonly used white pigments such as titanium dioxide, fillers, and the like. A small amount of an additive may be added. The support for image material coated with the polyolefin resin of the present invention can be used for color photographic paper, black-and-white photographic paper.

  Examples of the present invention will be described below, but the present invention is not limited to these examples. In addition, “parts” shown in the examples represents parts by mass of the substantial solid content.

(Production of Pulp A)
The LBKP pulp was diluted to a pulp solid content of 4% by mass, beaten to a freeness of 440 ml CSF, and then diluted to a pulp solid content of 1% by mass to obtain a pulp slurry. An appropriate amount of sodium carbonate and an appropriate amount of sulfuric acid were added to the pulp slurry thus obtained to adjust the pH to 7.0. Thereafter, 100 parts of pulp solids was added with talc as an inorganic pitch control agent in an amount of 0.00. A sample of pulp A was obtained by adding 05 parts.

(Preparation of pulp B)
In pulp A, a sample of pulp B was prepared in the same manner as pulp A, except that 1 part of talc was added as an inorganic pitch control agent.

(Production of Pulp C)
In pulp A, a sample of pulp C was prepared in the same manner as pulp A, except that 0.01 part of talc was added as an inorganic pitch control agent.

(Preparation of pulp D)
In pulp A, a sample of pulp D was prepared in the same manner as pulp A, except that 2.5 parts of talc was added as an inorganic pitch control agent.

(Production of Pulp E)
In the pulp A, a sample of the pulp E was prepared in the same manner as the pulp A except that talc as an inorganic pitch control agent was not added.

(Preparation of Pulp F)
In Pulp A, a sample of Pulp F was prepared in the same manner as Pulp A except that an appropriate amount of sodium carbonate and an appropriate amount of sulfuric acid were added as pH adjusting agents to adjust the pH to 6.5.

(Production of pulp G)
In Pulp A, a sample of Pulp G was prepared in the same manner as Pulp A, except that an appropriate amount of sodium carbonate and an appropriate amount of sulfuric acid were added as pH adjusting agents to adjust the pH to 6.0.

(Preparation of pulp H)
In the pulp A, a sample of the pulp H was prepared in the same manner as the pulp A except that clay was used instead of talc as the inorganic pitch control agent.

(Production of Pulp I)
In Pulp A, Pulp I was prepared in the same manner as Pulp A, except that an organic pitch control agent (Polystar OM: NOF Corporation) was used instead of talc as the pitch control agent.

Example 1
Pulp A 100 parts light calcium carbonate (specific gravity 0.52) as the amount of pulp (indicated by ash content in base paper)
"Tama Pearl 121" manufactured by Okutama Industry
Addition-adjusted cationized starch so that the content in paper is 1% by mass
Nippon Food Processing "Neotac 40T" 2 parts cationic AKD sizing agent
"AD1608" made by Seiko PMC 0.4 parts higher fatty acid sizing agent
"NS-815" manufactured by Modern Chemical Industry Co., Ltd. 0.15 part yield improver
“PL1610” made by Eka Chemicals 0.01 parts Papermaking temperature was set to 50 ° C., pulp and internal chemicals were adjusted according to the above composition, paper was made with a long net paper machine, and after paper making, a calendar process was performed, and a basis weight of 80 g / An m ² paper was produced and used as the sample of Example 1. The pH of the pulp slurry at this time was 7.9.

(Example 2)
A sample of Example 2 was prepared in the same manner as in Example 1 except that the addition amount of the cationic AKD sizing agent was 1 part in Example 1. The pH of the pulp slurry at this time was 8.03.

(Example 3)
A sample of Example 3 was prepared in the same manner as in Example 1 except that the amount of the cationic AKD sizing agent added was 0.1 part in Example 1. The pH of the pulp slurry at this time was 7.95.

Example 4
A sample of Example 4 was produced in the same manner as in Example 1 except that pulp B was used instead of pulp A in Example 1. The pH of the pulp slurry at this time was 8.02.

(Example 5)
A sample of Example 5 was produced in the same manner as in Example 1 except that pulp C was used instead of pulp A in Example 1. The pH of the pulp slurry at this time was 8.01.

(Example 6)
A sample of Example 6 was produced in the same manner as in Example 1 except that pulp F was used instead of pulp A in Example 1. The pH of the pulp slurry at this time was 7.54.

(Example 7)
In Example 1, instead of using the cationic AKD sizing agent, an anionic AKD sizing agent (“Size Pine K-910” manufactured by Arakawa Chemical Industries, Ltd.) was used. A sample of was prepared. The pH of the pulp slurry at this time was 8.01.

(Example 8)
A sample of Example 8 was prepared in the same manner as in Example 7 except that the amount of the anionic AKD sizing agent added was 1 part in Example 7. The pH of the pulp slurry at this time was 8.06.

Example 9
A sample of Example 9 was prepared in the same manner as in Example 7 except that the amount of the anionic AKD sizing agent added was 0.1 part in Example 7. The pH of the pulp slurry at this time was 7.9.

(Example 10)
In Example 1, a sample of Example 10 was produced in the same manner as in Example 1 except that 0.1% by mass of soda ash was added to 100% by mass of pulp instead of calcium carbonate. The pH of the pulp slurry at this time was 7.86.

(Example 11)
A sample of Example 11 was produced in the same manner as in Example 1 except that pulp H was used instead of pulp A in Example 1. The pH of the pulp slurry at this time was 7.85.

Example 12
A sample of Example 12 was prepared in the same manner as in Example 1 except that the amount of light calcium carbonate added in Example 1 was adjusted so that the content in paper was 5% by mass. . The pH of the pulp slurry at this time was 8.30.

(Comparative Example 1)
A sample of Comparative Example 1 was prepared in the same manner as in Example 1 except that the amount of cationic AKD sizing agent added was 1.5 parts in Example 1. The pH of the pulp slurry at this time was 8.03.

(Comparative Example 2)
In Example 1, a sample of Comparative Example 2 was prepared in the same manner as in Example 1 except that the cationic AKD sizing agent was not added. The pH of the pulp slurry at this time was 7.94.

(Comparative Example 3)
In Example 1, a sample of Comparative Example 3 was produced in the same manner as in Example 1 except that pulp D was used instead of pulp A. The pH of the pulp slurry at this time was 8.03.

(Comparative Example 4)
A sample of Comparative Example 4 was produced in the same manner as in Example 1 except that Pulp E was used instead of Pulp A in Example 1. The pH of the pulp slurry at this time was 7.9.

(Comparative Example 5)
In Example 1, a sample of Comparative Example 5 was produced in the same manner as in Example 1 except that pulp G was used instead of pulp A. The pH of the pulp slurry at this time was 7.32.

(Comparative Example 6)
In Example 1, a sample of Comparative Example 5 was produced in the same manner as in Example 1 except that Pulp I was used instead of Pulp A. The pH of the pulp slurry at this time was 7.92.

<Sizing evaluation>
The resulting base paper for support was conditioned for 8 hours in an environment of 23 ° C. and 65% RH, then corona-treated on both sides, and melt-extruded low density polyethylene with an extruder to cover 30 g / m ² Thus, an image material support was prepared, and the penetration from the image material support cut surface was evaluated for each image material support by the following test method.

<Penetration test method>
A solution of benzyl alcohol: diethylene glycol: rose bengal = 100: 100: 1 was prepared, and the temperature was adjusted to 20 ° C. to obtain an evaluation solution. The prepared support for image material was conditioned for 8 hours in an environment of 23 ° C. and 65% RH, and then cut into 5 × 5 cm using a cutter to prepare a sample. The cut sample was immersed in the evaluation solution for 3 minutes, immediately after being taken out, washed with water and immediately wiped off with water to prevent the evaluation solution from penetrating into the sample more than necessary. The distance at which the red dye can be confirmed was measured from the cutting edge of the sample. The penetration degree of less than 0.5 mm was evaluated as ◯, the penetration degree of 0.5 mm or more and less than 0.8 mm was evaluated as Δ, and the penetration degree of 0.8 mm or more was evaluated as ×. A product suitable for a product has a rating of Δ or higher.

<Foreign matter defect evaluation>
The obtained base paper was subjected to a foreign matter defect evaluation by visually checking the prepared sample to determine whether or not a foreign matter defect had occurred. ◎ if there are no defects, ◯ if there is one foreign object defect of 0.5 x 0.5 mm or more, △ if there are two foreign object defects, △ if there are three or more foreign object defects What was there was marked with x. A product suitable for a product is one having an evaluation of Δ or more.

<Result evaluation>
As a result of comparing Examples 1, 2, and 3 and Comparative Examples 1 and 2, in the case of Comparative Example 1 in which 1.5 parts of the AKD sizing agent was excessively added, foreign matter defects increased. Moreover, in the case of the comparative example 2 which does not add an AKD sizing agent, it is inferior to size property. On the other hand, in Examples 1, 2, and 3 in which 0.1 to 1 part of AKD sizing agent was added, a base paper having excellent sizing properties and few foreign matter defects can be produced.

  As a result of comparing Examples 1, 4, and 5 with Comparative Examples 3 and 4, both the comparative example 3 in which talc is added excessively and the comparative example 4 in which talc is not added increase foreign matter defects. This is presumably because when the talc is excessively added, foreign matter defects due to aggregation with the sizing agent increase, and when no talc is added, the foreign matter defects derived from pitch increase. On the other hand, in Examples 1, 4, and 5 in which 0.01 to 1 part of talc was added, a base paper having excellent size characteristics and few foreign matter defects can be produced.

  As a result of comparing Examples 1 and 6 with Comparative Example 5, in the case of Comparative Example 5 in which the pH of the pulp slurry is adjusted to less than 7.5, the foreign matter defects increase. On the other hand, in Examples 1 and 6 in which the pH of the pulp slurry was adjusted to 7.5 or more, a base paper having excellent size characteristics and few foreign matter defects can be produced.

  As a result of comparing Examples 1 to 3 and 7 to 9, the use of an anionic AKD sizing agent as an AKD sizing agent has fewer foreign matter defects than when a cationic AKD sizing agent is used. In addition, there is no significant difference in size.

  As a result of comparing Examples 1 and 10, the use of calcium carbonate as a pH adjuster has fewer foreign matter defects than when sodium carbonate (soda ash) is used. In addition, there is no significant difference in size.

  As a result of comparing Examples 1 and 11 with Comparative Example 6, in the case of Comparative Example 6 using an organic pitch control agent as the pitch control agent, foreign matter defects increase. In addition, when talc is used as the inorganic pitch control agent, foreign matter defects are most reduced. There is no significant difference in size.

  When Examples 1 and 12 are compared, the larger the amount of calcium carbonate added as a pH adjuster, the smaller the size. There is no significant difference in terms of foreign matter defects.

  INDUSTRIAL APPLICABILITY The present invention can provide a base paper for a support that is excellent in size and has few foreign matter defects.

Claims (4)

  In a base paper for a support used for a support for an image material in which both sides of a paper substrate are coated with a polyolefin resin, an inorganic pitch control agent is added to the pulp slurry used for the base paper as a pitch control agent in an amount of 0.00. 01 to 1% by mass, 0.1 to 1% by mass of an alkyl ketene dimer as an internally added sizing agent, 0.05% by mass or more of an inorganic pH adjuster as a pH adjuster, and the pH of the pulp slurry during papermaking Is a base paper for a support, characterized in that it is 7.5 or more.   The base paper for a support according to claim 1, wherein the inorganic pH adjuster is calcium carbonate.   The base paper for a support according to claim 1 or 2, wherein the internally added sizing agent is an anionic alkyl ketene dimer.   In a base paper for a support used for a support for an image material in which both surfaces of a paper substrate are coated with a polyolefin resin, an inorganic pitch control agent is used as a pitch control agent in a pulp slurry used for the base paper as a pitch control agent to 0.01. ~ 1% by mass, 0.1 to 1% by mass of alkyl ketene dimer as an internal sizing agent, 0.05% by mass or more of an inorganic pH adjuster as a pH adjuster, and the pH of the pulp slurry during papermaking A method for producing a base paper for a support, characterized in that the paper is made to be 7.5 or more.