FI74080C - A new, effective neutral glue - Google Patents

Description

74080

New, effective neutral glue

The invention relates to an effective substantially filler-free neutral paper adhesive consisting of an aqueous dispersion of a hydrophobic, cellulose-reactive sizing agent.

Various additives are used to increase the water repellency of the paper, i.e. the degree of hydrophobization. When a traditional resin-adhesive and alum sizing mixture is used, the production of paper products takes place under acidic conditions. In this case, the disadvantages are, among other things, that the resin adhesive and alum adversely affect the strength properties, brightness and resistance to aging of the paper and that the acidity promotes corrosion. Em. for these reasons, interest in the manufacture of paper products containing adhesives under neutral and even alkaline conditions has grown strongly. A common feature of suitable synthetic pulp adhesives is that, unlike resin adhesives, they react with cellulose molecules to form a highly permanent adhesive due to chemical covalent bonds.

"Paper product" as used herein means sheet-like, web-like or molded products made from fibrous cellulosic materials. They also include similar mixtures of cellulose and other material, such as synthetic material or mineral fiber. In addition to the actual cellulose, the "paper product" may contain varying amounts of mechanical or chemimechanical pulp as well as mineral fillers (such as kaolin, talc, CaCO and TiO).

3 2

Hydrophobic compounds containing groups reactive with cellulose hydroxyls have proven to be good neutral adhesives. Of the synthetic neutral adhesives well known in the art, e.g. long-chain fatty acid derivatives of ketene dimers, carboxylic acid anhydrides, organic isocyanates and carbamoyl chloride 2,74080 (FI Publication No. 64,677, U.S. Patent No. 4,279,794 and INSKO 159-81 VIII, p. 17). In addition, fatty acid clumping compounds with chromium or aluminum compounds, long-chain N-substituted aziridine derivatives, long-chain thermoplastic copolymers and some condensation-type thermosetting resins have been mentioned (U.S. Pat. No. 3,575,796).

Synthetic neutral adhesives have e.g. the following advantages: - A neutral or slightly alkaline process gives a paper with better strength properties, stability, aging properties, some printability properties, enhanced effect of optical brighteners and gluing resistance.

- Alkaline grinding has in some cases been found to save energy and favor the development of strength.

- Surface dyeing of the paper product is possible.

- The glue adheres almost completely so the circulating water remains free of glue.

But synthetic neutral adhesives also have their own disadvantages. Thus - synthetic adhesives (especially ketene dimer-based adhesives) mature much more slowly than traditional resin adhesives, - mucus and foam formation may occur in the process, and e.g. sticking problems. Microbiological activity is increased under neutral conditions, - synthetic neutral adhesives most often require cationic retention aids or accelerators which may have adverse effects on sheet formation and other wet end phenomena.

In order to eliminate these disadvantages and to increase the efficiency of gluing, new adhesive-retention agent-accelerator combinations have been invented, as well as more efficient ratios of these components. In general, adhesive dispersions contain cationic starch as a stabilizer. A cationic polymer is used as a retention agent or accelerator for gluing. FI patent publication 64 677, US patent publication 3 74080 4 279 794 and FI publication publication 677 35 disclose a number of cationic polymers for use as retention aids or accelerators, such as cationic starch, polynomalactan, polyethylamine, polyamine amine, polyamine, polyamide, polyamide (diallylamine) and bis-aminopropylpiperazine epihalohydrin, as well as cationic melamine, urea and guanidine formaldehyde resins. It has also been suggested that an anionic polymeric binder be used in addition to the cationic polymeric retention aid (FI Publication 67,735 and TAPPI Notes, 1985 Alkaline Papermaking, page 15).

Prior art methods for preparing an adhesive emulsion have paid attention to the composition of the substance and the stability of the resulting emulsion. Synthetic hydrophobic adhesives are usually solids, so they must be melted before emulsification. This can be done in a separate melting vessel or by mixing the solid adhesive with a hot starch solution. The still hot emulsion is then rapidly homogenized. According to the methods of patent publications FI-64 677 and US-4 279 794, this takes place at a pressure of 290 bar in the homogenizer 11a. According to TAPPI (TAPPI Notes, Alkaline Papermaking, TAPPI PRESS, Atlanta, page 15), homogenization is performed under laboratory conditions using a laboratory ultrasonic homogenizer for two minutes to obtain a stable suspension with a total solids content of 0.5% by weight and a particle size of is 0.3 μm. The particle sizes of commercial products, according to this publication, range from 0.3 to 0.8 jun.

It has now quite surprisingly been found that the aforementioned hydrophobic neutral adhesives which react with cellulose are much more effective if their particle sizes in the dispersion are larger than before when used in the production of substantially filler-free paper or board. Substantially filler-free paper or board in this case means a product with a filler content of less than 10%. Thus, in accordance with the present invention, a neutral adhesive is provided which makes the paper highly hydrophobic by producing the adhesive 4 74080 so that the particle sizes in its dispersion are considerably larger than in the neutral adhesives to date. Thus, if desired, the hydrophobicity of the paper can be increased by using the same amount of adhesive as before, or the above-mentioned disadvantages of synthetic adhesives can be reduced by using smaller amounts of adhesive than before.

The effective paper neutral adhesive according to the invention is characterized in that the size of the particles in the dispersion of the hydrophobic sizing agent which is reactive with cellulose is about 1 to 100 μm. It is most preferred to use particles having a size of about 5-40. The reactive sizing agent is preferably a long chain ketene dimer, a carboxylic acid anhydride, an organic isocyanate or carbamoyl chloride. The neutral adhesive preferably also contains a cationic polymeric retention aid and optionally also an anionic polymeric binder.

Adhesives useful in the invention are based on hydrophobic, cellulose-reactive substances such as long chain ketene dimers, dicarboxylic acid anhydrides, organic isocyanates and carbamoyl chlorides. These substances make the paper product hydrophobic by reacting with the cellulose in the paper product. The following are a few hydrophobic, cellulose-reactive sizing agents which can be advantageously used in the preparation of the neutral sizing agent according to the invention.

Alkyl ketene dimers (AKD) have the general formula / r-ch = c = o7 (i) 2 wherein R is a hydrocarbon group such as alkyl of at least 8 carbon atoms, cycloalkyl of at least 6 carbon atoms, aryl, aralkyl or alkaryl. Examples of ketene dimers include octyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl, eicosyl, docosyl, tetracosyl, phenyl, 5,74080 benzyl-beta-naphthyl and cyclohexyl ketene dimers, as well as keters containing montanic acid Posta, naphthenic acid, delta-9,10-decylenic acid, delta-9,10-dodecylenic acid, palmitoleic acid, oleic acid, ricinoleic acid, linseed oleic acid such as rasolene acid and oleostearic acid, of mixtures obtained from coconut oil, babassu oil, palm kernel oil, palm oil, olive oil, peanut oil, rapeseed oil, beef tallow, lard or leaf whale fat. Mixtures of all the above fatty acids with each other can also be used.

Useful acid anhydrides include (A) resin anhydride, cf. U.S. Patent 3,582,464, (B) anhydrides having the structural formula R 1 - C = O (II) 2 'R - C = 0 1.2 wherein R and R may be the same or different saturated or unsaturated hydrocarbon groups which are straight chain or branched alkyl groups, aromatic substituted alkyl groups or alkyl-substituted aromatic groups containing 11 to 39 carbon atoms, and (C) cyclic dicarboxylic anhydrides of the formula

c = O

4 R, R (R) p (III) c = o wherein R represents a dimethylene or trimethylene group and R1 is a hydrocarbon group containing R-22 carbon atoms and which is alkyl, alkenyl, aralkyl or aralkenyl. Thus, cyclic anhydrides are substituted succinic or glutaric anhydrides. Typical examples of straight chain anhydrides are myristoyl anhydride, palmitoyl anhydride, oleoyl anhydride and stearoyl anhydride. Typical examples of cyclic anhydrides are isooctadecenyl succinic anhydride, m-hexadecenyl succinic anhydride, octenyl succinic anhydride and octyl glutaric anhydride.

Organic isocyanates are useful when their hydrocarbon chains contain at least 12 carbon atoms, preferably 14 to 36 carbon atoms. Such isocyanates include resin isocyanate, dodecyl isocyanate, octadecyl isocyanate, tetradecyl isocyanate, 6-ethyldecyl isocyanate, 6-phenyldecyl isocyanate, and polyisocyanates such as 1,18-octadecyl diocyanate. isocyanate having one long chain alkyl group per two isocyanate groups which gives the whole molecule its hydrophobic properties.

The formula for carbamoyl chlorides is

R1 O

N - C

/ 'R2 Cl (IV) 1 2 wherein R and R are long chain groups, preferably stearyl groups (INSKO 159-81 VIII).

In general, sizing dispersions contain cationic starch as a stabilizing agent, but other protective colloids well known in the art may also be used.

Synthetic adhesives often require a cationic retention aid to initially attach to the fibers, and an accelerator may be used to accelerate the sizing reaction. Such retention aids or accelerators include cationic polymers such as cationic starch; cationic mannogalactan; melamine, 7,74080 niformalyl resins; urea-formaldehyde resins; guanidine forma lyylihartsit; alkylene polyamine halohydrin resins · amino resins; dicyandiamide-formaldehyde-amine polymers; urea mono-substituted urea resins; polyaraiini-polyamide polymers; cationic acrylamide polymer; sulfonated dimethylol urea resins; aminosulphuric-melamine-formaldehyde resins; cellulose swelling amine oxide; polyamiinipolyamidihalohydriinihartsit; cationic polyamine; disyaanidiamidiformaldehydihartsit; a resinous mixture resulting from the reaction of a dicyandiamide, an ammonium salt, a formaldehyde and an acid salt of a water-soluble aminopolyamide; acid-lyeteeniimiini; poly (diallylamino) epihalohydrin; a resin resulting from the reaction of dicyandiamide or cyanamide, bis-aminopropylpiperazine and epihalohydrin; and poly (bis-aminopropylpiperazine) epihalohydrin resin. In addition to the cationic retention aid or accelerator, an anionic polymeric binder can also be used.

The method according to the invention consists of several steps known per se, which are combined to obtain a dispersion of a hydrophobic adhesive in which the particles are considerably larger than before. The dispersing solution is prepared by dissolving an emulsifier, which may preferably be cationic starch, and optionally other additives which facilitate dispersion and adjust the pH in hot water. A cellulose-reactive hydrophobic group-containing hydrophobic adhesive is then added, which may preferably be the above-mentioned ketene dimer derivative, acid anhydride, isocyanate or carbamoyl chloride. The temperature, pH, concentration of the solution, etc. are adjusted to the optimum. In the next step, emulsification is performed. In order to obtain the dispersion particle sizes according to the invention, emulsification conditions and equipment must be used at this stage to form large particles. For example, a rotor / stator type emulsifier is suitable for the purpose of the invention, with which considerably larger particles are obtained than, for example, the high-pressure homogenizer used for the production of adhesives according to the prior art. In the case of different adhesives, the conditions and equipment for preparing the dispersions may vary, but according to the invention they are always adjusted so that the sizes of the dispersed adhesive particles are considerably larger than before.

The following figures show photographs of adhesive dispersions taken under an electron microscope at 600x magnification.

Figure 1 shows an adhesive according to the invention.

Figure 2 shows a prior art adhesive containing the same active ingredient.

Figure 3 shows a commercial adhesive.

eXAMPLES

The following are examples of how the invention may be practiced.

The adhesive according to the invention (adhesive 1) was prepared as follows. 2 g of cationic starch (e.g. Posamyl E6) are slurried in 100 g of water and the mixture is stirred for 30 minutes at 95 ° C. The starch solution is cooled to 65 ° C, mixed with 10 g of ketene dimer prepared in a known manner from stearic and palmitic acid (ratio 1: 1) and the pH is adjusted to 2-3 with sulfuric acid. The mixture is emulsified with a rotor / stator type emulsifier (e.g. Ultra-Turrax, Jank & Kunkel KG) for 10 minutes and cooled to room temperature. The size of the ketene dimer particles of the emulsion prepared in this way was determined by electron microscopy (see Figure 1).

The prior art adhesive (adhesive 2) was prepared as follows. The premix is prepared in the same manner as in the present invention. However, the emulsification is carried out by passing the mixture 1 to 4 times through a high-pressure homogenizer (pressure difference 20 to 50 MPa). The particle size of the emulsion thus formed was determined by electron microscopy (see Figure 2).

9 74080

Adhesives according to the invention and the prior art were subjected to adhesive tests by determining a Cobb value and performing a drip test.

The Cobb value, i.e. the water absorption of the paper, refers to the amount of water that is absorbed by either surface of the paper in a given time from a 1 cm high water column evenly covering it. Since sizing is intended to increase the hydrophobicity of the paper, it follows that the lower the Cobb value, the better the sizing result. The Cobb method is described in more detail in SCAN-B 12:64. According to its principle, air-conditioned specimens are weighed both before and after they have been placed in contact with water under certain conditions. Before the latter weighing, the excess water is removed by squeezing the test pieces between the blotting papers with a brass roll of specified size and weight. In the case of Cobb values, the water absorption time used is also reported as a subscript. Thus, Cobb and Cobb mean that the water 60 60 absorption time has been 30 and 60 seconds, respectively.

According to the drip test, a drop of water is placed on the surface of the paper and the time it takes for the drop to absorb inside the paper is measured. Since it is a question of the absorption time, it follows that the higher the reading, the better the bonding. It is important for the papermaking process to achieve hydrophobicity as quickly as possible. Thus, the drip test is measured immediately after the paper is finished and Cobb after 10 minutes. These values describe the so-called instant-gluing, ie how fast the gluing matures (develops). Cobb Value No matured 60% measured after half an hour after the oven treatment (105 ° C) and the Cobb -1 weeks is measured one week of natural aging at 60 o (23 C, 50% RH). Both Cobb values 60 describe the final gluing.

Example 1 In this example, a pulp having a composition of 40% bleached pine cellulose 25 SR and 60% bleached birch cellulose (25 SR) having a pH of 7.5-8.0 was used. Glue 1 and glue 2 used the emulsifier Posamyl T \ 6 (high cationic starch, manufactured by Stadex). The ketene-dimer adhesive used was prepared as shown on page 8.

The results are shown in Table I.

Table I

Glue Glue Glue par- Drip test ^ obb ^ Q Co ^^ 60 Col:> ^ 6 0 dose,% particle size 10 min. week most ripened after ty

Glue 1 0.05 5-40> 60 19 22.4 21.1

Glue 1 0.07 5-40> 60 20 21.0 19.5

Glue 2 0.05 <1 3 80 31.9 24.0

Glue 2 0.07 <1 30 43 24 '° 22'1

Commercial 0.05 <1 0 130 140 60 product 0.07 <1 10-15 80 28.2 22.7 (Aqupel 3100)

Adhesive 2 is otherwise like adhesive 1, but its particle size is smaller, i.e. adhesive 1 is homogenized by passing it 2 times through a high-pressure homogenizer (pressure difference 400 bar) 2

Measured directly from the machine

Active ingredient,% of solids Example 2 The same conditions as in Example 1 were used in this example, except that Finna-myl Cat-15 (cationic starch, manufactured by Hämeen Peruna) was used as an emulsifier in adhesives 3 and 4. The only difference between the adhesives 3 and 4 is the particle size, i.e. the adhesive 4 is obtained by passing the adhesive 3 three times through a high-pressure homogenizer (pressure difference 40 MPa). The results are shown in Table II.

74080 11

Table II

Glue Glue Glue Drip test Cobb Cobb ^ Q Cobt> 60 servings,% particle 10 min 1 week after maturing size work jam

Glue 3 0.07 5-40 45 26 22.4 20.6

Glue 4 0.07 <1 0 135 150 140

As can be seen from the examples, the neutral adhesive of the present invention is faster and more effective than the neutral adhesives to date.

active substance,% of amount of active substance

Claims (4)

12 74080 An effective, substantially filler-free paper neutral adhesive consisting of an aqueous dispersion of a hydrophobic, cellulose-reactive sizing agent, characterized in that the size of the particles in the sizing agent dispersion is about 1 to 100. A neutral adhesive according to claim 1, characterized in that the size of the dispersion particles of the adhesive is about 5 to 40 μm. Neutral adhesive according to Claim 1 or 2, characterized in that the hydrophobic adhesive which is reactive with cellulose is an alkyl ketene dimer. Neutral adhesive according to one of the preceding claims, characterized in that it also contains a cationic polymeric retention aid and, if appropriate, also an anionic polymeric binder. I;