JPH0368158B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing acid-free paper that has excellent sizing properties immediately after papermaking. Conventionally, paper has been made in an acidic range around PH4.5 by adding an anionic rosin sizing agent and sulfuric acid as a fixing agent. In contrast, recent efforts have been made to use cheap calcium carbonate as a filler, use waste paper containing calcium carbonate, and improve the shelf life of paper. It became necessary to make acid-free paper. However, in the pH range of 7 or above, sulfuric acid band does not act effectively as a fixing agent for rosin size, so sizing with various neutral sizing agents is generally performed. Currently, commercially available neutral sizing agents include organic ketene dimers, types with reactive groups for cellulose such as substituted cyclic dicarboxylic anhydrides, epoxidized higher fatty acid amides, and cationized styrene-maleic anhydride copolymers. There is a type that fixes to anionic cellulose by making it tathionic, such as coalesced and cationized petroleum resins. Among these, substituted cyclic dicarboxylic acid anhydrides have problems with workability because they need to be emulsified immediately before addition, and cationic neutral sizing agents require the addition of a large amount of sizing agent to obtain the desired sizing degree. This causes problems such as paper strength reduction and process stains. Therefore, a neutral sizing agent containing an organic ketene dimer such as an alkyl ketene dimer as a main component can obtain a sufficient sizing degree by adding a small amount, and is excellent in terms of workability. However, organic ketene dimers do not develop sufficient size immediately after papermaking unless sufficient thermal energy is applied when drying the wet paper. It has the disadvantage of not showing any gender. For this reason, when used as various base papers to be coated with an aqueous smear solution using an air knife coater or the like immediately after papermaking, problems such as poor control of the smear amount, paper breakage, and wrinkles occur. In addition, if a large amount of organic ketene dimer is internally added in order to develop sufficient size properties immediately after papermaking, it not only reduces paper strength but also significantly reduces the coefficient of friction on the paper surface, leading to problems in the post-process. It causes It is known to internally add cationic starch or various reaction promoters together with the organic ketene dimer in order to improve the rise in size immediately after papermaking, which is a drawback of the organic ketene dimer. However, the effects of these size-related rise improving agents were not satisfactory. In addition, conventional surface sizing agents have been used for the purpose of reinforcing the size, but most of these agents are satisfactory immediately after paper making when applied to neutral paper with a single organic ketene dimer added internally. showed no size-related reinforcing effect. The present invention solves these problems in producing acid-free paper. The first object of the present invention is to provide a neutral paper that exhibits sufficient sizing properties immediately after papermaking under normal drying conditions of a paper machine. Second, by using a small amount of sizing agent, it is possible to resist neutral paper, which has less adverse effects on paper strength, whiteness, etc. due to sizing agent. In order to solve the above-mentioned problems with neutral paper, the present inventors have conducted extensive research on the use of various internal additives and surface sizing agents alone or in combination. By applying an aqueous solution of anionic styrene-acrylic copolymer to the surface of neutral paper containing a tertiary amine starch derivative and an organic ketene dimer, a small amount of sizing agent is sufficient immediately after papermaking. The inventors discovered that it is possible to obtain neutral paper that exhibits suitable size characteristics, and have completed the present invention. In addition, the degree of substitution added internally to neutral paper is 0.035 to 0.070.
Even if either the tertiary amine starch derivative or the organic ketene dimer is missing, the size properties of paper whose surface is sized with an aqueous solution of anionic styrene-acrylic copolymer immediately after papermaking and after aging was insufficient. Also, the degree of substitution is 0.035
Even when neutral paper containing ~0.070 of a tertiary amine starch derivative and an organic ketene dimer was treated with a surface sizing agent other than an aqueous solution of anionic styrene-acrylic copolymer, papermaking Immediately after this, no paper with sufficient size could be obtained. That is, the present invention involves surface sizing an aqueous solution of anionic styrene-acrylic copolymer onto neutral paper internally doped with a tertiary amine starch derivative with a degree of substitution of 0.035 to 0.070 and an organic ketene dimer. This is a unique method for producing acid-free paper. The third type with a degree of substitution of 0.035 to 0.070 used in the present invention
For example, starch derivatives are produced by reacting starch with ethyleneimine to obtain aminoethylated starch, by reacting starch with polyalkylene polyamine, or by reacting starch with polyalkylene polyamine.
- It is obtained by a method of reacting a halogenated amine such as dimethylaminoethyl chloride. As the basic starch, unmodified starches derived from all kinds of plant sources such as corn, corn, tapioca, and wheat, as well as modified starches obtained by mild oxidative conversion, oxygen conversion, or acid hydrolysis, can be used. I can do it. The degree of substitution (DS) of the tertiary amine starch derivatives suitable for use in the present invention, ie the average number of cationic groups per anhydroglucose unit of the starch molecule, is between 0.035 and 0.070. Many commercially available tertiary amine starch derivatives have a degree of substitution of 0.035 or less, and even when they are used, sufficient size effects cannot be obtained. Tertiary amine starch derivatives having a degree of substitution of 0.070 or more are undesirable because they have too strong cationic strength and produce fine foam-like aggregates during paper making. In addition, quaternary salts exhibit cationic properties even at pH 7 or higher.
Even with grade ammonium starch derivatives, satisfactory size effects could not be obtained. Examples of the organic ketene dimer in the present invention include U.S. Pat. No. 2,785,067, U.S. Pat.
−98997, JP-A-55-116898, JP-A-55-
No. 132799, JP-A-56-101998, JP-A-55-
A sizing agent based on an organic ketene dimer as described in No. 37639 can be used. The amount of the organic ketene dimer to be added is sufficient to control the amount of surface sizing liquid deposited, and is preferably 0.02 to 0.20% by weight based on the pulp. 0.02
If it is less than % by weight, the surface sizing liquid will penetrate to a large extent in a size press or the like, and not only will paper breakage easily occur, but also sufficient sizing properties will not be obtained. If it is more than 0.20% by weight, it is excessive and uneconomical for controlling the surface size liquid, and at the same time, the paper strength decreases, which is not preferable. The aqueous solution of anionic styrene-acrylic copolymer used in the present invention includes (a) a styrene monomer selected from the group consisting of styrene and styrene derivatives, and (b) acrylic acid, methacrylic acid, and acrylic acid ester. It is an aqueous liquid of a copolymer whose main component is an acrylic monomer selected from the group consisting of , and methacrylic acid ester.
No. 55-99909, Special Publication No. 12002, Special Publication No. 53-
This is a surface sizing agent described in No. 4123 and Japanese Patent Publication No. 54-33284. The aqueous solution of the anionic styrene-acrylic copolymer of the present invention can be used alone or in combination with starch, polyvinyl alcohol, latex, pigment, dye, etc. As a method for surface sizing, an apparatus capable of on-machine smearing such as a size press, gate roll coater, bill blade coater, etc. can be used. The neutral paper in the present invention is paper that is made at a pH of 7 to 9, rather than around 4.5 like conventional acidic paper. The neutral paper contains additives normally used in paper making, such as fillers, dyes, dry paper strength enhancers, wet paper strength enhancers, size fixing agents, retention improvers, etc., as necessary. It is also possible to contain a small amount of water-soluble aluminum salt in the paper. As in the present invention, by surface sizing an aqueous solution of anionic styrene-acrylic copolymer on neutral paper internally doped with a tertiary amyl starch derivative with a degree of substitution of 0.035 to 0.070 and an organic ketene dimer. It is possible to obtain neutral paper that exhibits sufficient sizing properties immediately after papermaking by using a small amount of internally added sizing agent. The present invention will be described in detail below with reference to Examples. Note that the present invention is not limited to the examples. In the Examples, all parts and percentages are by weight. Example 1 A paper with a basis weight of 60 g/m ² containing the following components in the following content was handmade, and after applying a wet pressure of 7.0 kg/cm ² to the wet paper,
It was dried for 45 seconds in a cylindrical dryer at 80°C. A mixture of hardwood bleached kraft pulp and softwood bleached kraft pulp beaten to 350 ml with a beater at Canadian standard freeness in a weight ratio of 8:2: 100 parts heavy calcium carbonate (Hydrocarb 60 manufactured by Shiraishi Calcium Co.): 10 parts talc ( (manufactured by Hyogo Talc Co., Ltd.): No. 3 prepared by the method of the modification example described below so that the degree of 10-part substitution was changed to three levels: 0.035, 0.050, and 0.070.
grade amine starch derivative: 0.50 parts An alkyl ketene dimer sizing agent (Haakon W manufactured by Deitz Hercules) was added so that the alkyl ketene dimer content was 0.10 parts. Note that 70% of the solid content of Haakon W is alkyl ketene dimer. The obtained handmade paper was subjected to size press treatment with a surface size liquid containing the following components in the following contents, and dried for 20 seconds in a cylindrical dryer at 80°C to obtain a sample. Water: 93.85 parts Oxidized starch (MS-3800, manufactured by Nihon Shokuhin Kogyo Co., Ltd.): 6 parts Anionic styrene-acrylic copolymer aqueous solution (Coropal M-150, manufactured by Seiko Kagaku Co., Ltd.) 0.15 parts Depending on the degree of substitution of the tertiary amine starch derivative, 1-2,
1-3 and 1-4. Example 2 Samples were prepared in the same manner as in Example 1 except that the degree of substitution of tertiary amine starch was 0.050 and the amount of alkyl ketene dimer added was changed to four levels: 0.01, 0.02, 0.20, and 0.30 parts. Obtained.
Due to the difference in the amount of alkyl ketene dimer added to these samples, 2-2, 2-3, and 2-
4, and 2-5. Comparative Example 1 Samples were obtained in the same manner as in Example 1 except that the degree of substitution of the tertiary amine starch derivative was changed to two levels, 0.030 and 0.080. These samples are designated as 1-1 and 1-5, respectively. Comparative Example 2 A sample was obtained in the same manner as in Example 1 except that a quaternary ammonium starch derivative having a degree of substitution of 0.050 was added instead of the tertiary amine starch derivative. This sample is designated as 1-6. Comparative Example 3 A sample was obtained in the same manner as in Example 1 except that the amount of tertiary amine starch derivative added was 0 parts. This sample is designated as 1-7. Comparative Example 4 A sample was obtained in the same manner as in Example 2 except that the alkyl ketene dimer sizing agent was not added. This sample is designated as 2-1. Comparative Example 5 The unsize-pressed handmade paper internally added with tertiary amine starch with a degree of substitution of 0.050 in Example 1 was subjected to size-press treatment with a surface size liquid containing the following components in the following contents, and the same paper as in Example Samples were obtained using the method. Water: (total amount after addition of additives is 100 parts) Oxidized starch (MS-3800 manufactured by Nihon Shokuhin Kogyo Co., Ltd.): 6 parts Surface sizing agent (additive-free, petroleum resin-based, and maleic anhydride-diisobutylene-based) ): 0.15 part
1, 3-2, and 3-3. All of the above surface sizing agents are commercially available products, and their trade names are as follows. Petroleum resin type (Coropal P- manufactured by Seiko Kagaku Co., Ltd.)
110SS) Maleic anhydride-diisobutylene system (Aquastar HR-303 manufactured by Hitachi Chemical Co., Ltd.) Example of modification of starch 120 parts of corn starch are slurried in 1880 parts of water containing 48 parts of sodium hydroxide. Beta-diethylaminoethyl chloride is added to this slurry depending on the degree of substitution required. The resulting mixture is then placed in a continuous steamer whose contents are adjusted to a temperature of approximately 150 degrees Celsius.
Pass at a flow rate of 100 c.c./min. The solid content of the obtained tertiary amine starch derivative dispersion was 6%.
It is. When producing a quaternary ammonium starch derivative, it can be obtained by adding 3-chloro.2-hydroxypropyltrimethylammonium chloride instead of beta-diethylaminoethyl chloride. The above results are summarized in Table 1.

【table】

[Table] From Table 1, it can be seen that the surface size liquid containing the anionic styrene-acrylic copolymer lacks either the tertiary amine starch derivative with a degree of substitution of 0.035 to 0.070 or the organic ketene dimer. It can be seen that not only does the amount increase and its adjustment become difficult, but also that the size properties immediately after papermaking become insufficient. In addition, when neutral paper internally added with a tertiary amine starch derivative with a degree of substitution of 0.035 to 0.070 and an organic ketene dimer is treated with a surface sizing agent other than an aqueous solution of anionic styrene-acrylic copolymer. It can be seen that good size properties cannot be obtained immediately after paper making. From the above results, the third type with a degree of substitution of 0.035 to 0.070
By applying an aqueous solution of anionic styrene-acrylic copolymer to the surface of neutral paper containing a grade amine starch derivative and an organic ketene dimer, the paper has good sizing properties immediately after papermaking and sufficient paper strength. It is clear that the paper obtained with

Claims (1)

[Scope of Claims] 1. An aqueous solution of anionic styrene-acrylic copolymer is surface sized on neutral paper internally added with a tertiary amine starch derivative and an organic ketene dimer with a degree of substitution of 0.035 to 0.070. A method for producing acid-free paper characterized by the following. 2. Claim 1, wherein the amount of organic ketene dimer added is 0.02 to 0.20% by weight based on the pulp.
Method for producing acid-free paper as described in Section 1.