DE3819968A1 - Process for preparing a surface sizing agent - Google Patents

Abstract

The preparation of the surface sizing agent for paper and board is effected by modifying 1.0 mol parts of an alternating alpha-methylstyrene-maleic anhydride copolymer which contains anhydride groups with from 0.7 to 1.0 mol parts of an aliphatic amine and from 0.9 to 1.2 mol parts of ammonia. According to the invention, a stirred vessel is charged with from 11 to 33 mol parts of water. At 10 to 80@C a 20 to 60% strength acetonic solution of alpha-methylstyrene copolymer as obtained by the free radical polymerisation of molar amounts of alpha-methylstyrene with maleic anhydride in acetone is stirred in. The acetone is then distilled off. Thereafter the aliphatic amine and ammonia are added as a mixture. After the dissolving of the polymer, the acetone still enclosed in the polymer is driven off. Thereafter the size is adjusted in a conventional manner with water to the desired size concentration. The advantage of the process is the avoidance of not only apparatus- but also labour-intensive powder technology.

Description

The invention relates to a process for the preparation of Surface sizing agents based on modified alpha-methyl styrene-maleic anhydride copolymers.

It is known that modified maleic anhydride copoly merisate used for the production of paper sizes become. The conversion of the anhydride group in the copolymer in the Halbamid is procedurally not easy.

If one starts from an acetone copolymer solution and ver substitutes with an amine or an aqueous amine solution, so the polymer precipitates as a sticky mass, which is when stirring together.

After DD 2 24 855 this process step is solved so that First, the polymerization of the Removed copolymer and the resulting copolymer powder in suspended in a mixture of water and amine. Below 303 K the suspension is stable. When the temperature is exceeded the suspension contracts to a lump. There at the amidation a considerable heat of reaction is free must the amidation very slowly and with removal of the reac tion heat done. After the amidation is the Half amide converted with ammonia water in the ammonium salt.

Experiments have shown that maximum in the amidation step 50% of the added amine reacts to the amide and the remainder is bound as a salt. When adding NH₄OH takes place  then with the unreacted anhydride groups in the polymer an amide formation to NH₂ amide. This creates a glue with inhomogeneous composition.

Another shortcoming is the required Ab separation of the polymer from the polymer solution. The recovery of the polymer powder via elaborate Ab separation and drying processes. Technically, this sets requires and leads to a high level of apparatus and operating costs thus to a worsening of the economy of Gesamtver driving the paper glue production.

The object of the invention is a method for the production a surface sizing agent for paper and cardboard the basis of alpha-methylstyrene-maleic anhydride copoly meren bypassing a complex solid insulation and solids drying without reducing the glue quality.

The invention is based on the object, alternating built-alpha-methylstyrene-maleic anhydride copolymers to amidate by reaction with an aliphatic amine and with ammonia to convert into the ammonium salts, without isolate the starting polymer and make it an effective To produce surface sizing agents for cardboard and paper len.

The task is accomplished by modifying 1.0 mole parts Anhy containing alternately constructed alpha-Me methylstyrene-maleic anhydride copolymer with 0.7 to 1.0 Mole parts of an aliphatic amine and 0.9 to 1.2 molar Share ammonia dissolved by, according to the invention in a Agitator 11 to 33 mol parts, preferably 16 to 22 mol parts Parts, water and at 10 to 80 ° C, preferably 20  up to 30 ° C, a 20 to 60% solution of alpha-acetone Methylstyrene copolymer, as after the radical Polymerization of molar amounts of alpha-methylstyrene and Maleic anhydride is obtained in acetone, stirred, then the acetone distilled off, then the aliphatic amine and adding ammonia as a mixture and after dissolving the Polymers which was still included in the polymer Ace ton abters and then in known per se Make the glue with ammonia water at a pH of 9.5 to 10 and with water to the desired glue concentration established.

As the aliphatic amine is advantageously n-butylamine used.

With the method according to the invention, the tedious and elaborate solid insulation and solids drying avoided and a homogeneous surface sizing agent of obtained high quality.

As alpha-methylstyrene-maleic anhydride copolymer A 50% solution of acetone was used radical polymerization of molar amounts of alpha-methyl styrene and maleic anhydride in acetone. The average molecular weight was 30,000.

Example 1

400 g of water are placed in a stirred vessel and on Tempered at 25 ° C. With stirring, 240 g of a 50% acetonic solution of alpha-methylstyrene Maleic anhydride copolymers are metered in, with a Polymer suspension arises. At a vacuum of 53.33 kPa and a bottom temperature of 70 to 80 ° C, the acetone distilled off from the aqueous phase. After that, the approach becomes  cooled to 45 to 50 ° C and to the aqueous suspension a mixture of 41 g of n-butylamine and 50 ml of NH₄OH (25%) given. After dissolving the polymer is at a vacuum of 53.33 kPa and a bottom temperature of 70 to 80 ° C the Residual acetone content distilled off from the glue solution. in the Following this are 15 ml of NH₄OH (25%) and 80 g of water added. This gives 645 g of glue solution.

Leimkennwerte Solids | 25.2% density 1.057 g / cm³ viscosity 152 cP PH value 9.5 iodine color 4 acetone content 0.04% Butylamidgehalt 79 mol% Degree of sizing (f) 1.2

example 2

300 g of water are placed in a stirrer and 25 tempered to 30 ° C. With stirring, 240 g of a 50% acetone alpha-methylstyrene-maleic anhydride Copolymer solution added. At a vacuum of 53.33 kPa and a bottom temperature of 80 ° C ge in ge dissolved acetone aborted. After completion of the distillation is the batch is cooled to 40 to 45 ° C and a mixture of 28 g n-butylamine and 65 ml ammonia water (25%) added. While heating to about 60 ° C, the Po dissolves on polymers. After dissolution of the polymer is the Residual acetone content at 53.33 kPa and 80 ° C sump temperature distilled off. Following the distillation, 15 ml Ammonia water (25%) and 70 ml of water added. This gives 645 g of glue solution  

Leimkennwerte Solids | 22.5% density 1.062 g / cm³ viscosity 62.5 cps PH value 9.65 iodine color 4 acetone content 0.07% Butylamidgehalt 62 mol% Degree of sizing (f) 1.3

Comparative example Powder preparation

240 g of the 50% acetone alpha-methylstyrene maleic acid anhydride copolymer solution are in a thin Layer applied to sheets and 10 hours in Vacuum drying oven dried at 100 ° C. On the sheets remains a powdery alpha-methylstyrene Maleic anhydride copolymer containing about 0.5% acetone contains.

glue production

424 g of water and 41 g of n-butylamine are placed in a stirred vessel submitted. At 25 to 30 ° C will be within 90 minutes 120 g of alpha-methylstyrene-maleic anhydride copolymer Powder added, whereby by cooling the Reaction temperature is maintained at values below 35 ° C. in the Connection to the powder dosing is 2 hours at 30 to 35 ° C stirred. Thereafter, 62 ml NH₄OH (25%) todo Siert and the contents of the flask for 2 hours at 60 ° C stirred.  

Leimkennwerte Solid content | 25% density 1.059 g / cm³ viscosity 160 cP PH value 9.8 iodine color 4 acetone content 0.06% Butylamidgehalt 76 mol% Degree of sizing (f) 1.3

Degree of sizing (f)

The determination of the degree of sizing (f) was carried out according to Albrecht (R. Korn and F. Burgsteller, paper and pulp testing, Springer Verlag 1953).

For the examination of the degree of sizing was a wood-free Standard paper with a basis weight of 80 g / m² used. The sizing concentration was 0.3% by weight in%. established.

Assessment of the degree of sizing

According to Albrecht, a good sizing is considered at a degree of sizing of f = 1 to 10, whereby the solids application should amount to 0.1 to 1 g / m 2 paper surface.

Claims (4)

1. A process for the preparation of a surface sizing agent for paper and cardboard by modifying 1.0 mole parts of anhydride-containing alternately synthesized alpha-methylstyrene-maleic anhydride copolymer with 0.7 to 1.0 mole parts of an aliphatic amine and 0, 9 to 1.2 parts by mole of ammonia, characterized in that 11 to 33 parts by mole of water are introduced in an agitator and at 10 to 80 ° C, a 20 to 60% strength acetone solution of alpha-methylstyrene Copo lymer, as obtained after radical polymerization mo larer amounts of alpha-methylstyrene and Maleinsäureanhy drid in acetone, stirred, then distilled off the acetone, then the aliphatic amine and ammonia added as a mixture and after the release of Po lymeren still included in the polymer Afterwards, the acetone is aborted and then, in a manner known per se, the glue is adjusted to a pH of 9.5 to 10 with ammonia water and to the desired level with water Setting glue concentration. 2. The method according to claim 1, characterized in that 16 to 22 mole parts of water are placed in the stirrer. 3. The method according to claim 1 and 2, characterized that the acetonic solution of the copolymer at 20 to 30 ° C is stirred into the water. 4. The method according to claim 1, 2 and 3, characterized net, that used as the aliphatic amine n-butylamine becomes.