MX2008008003A - Dry strength system for the production of paper and board - Google Patents

Abstract

The instant invention relates to certain cross-linked polyamides and their use in the paper and board industry for improving dry strength. The polyamide from the reaction of a di- or tri-primary amine with a di- or tri- or tetra carboxylic acid is further reacted with a di- or tri-functional cross-linking compound to give a cationic or anionic product with no reactive groups.

Description

OPTICAL MAMMALS FOR THE PRODUCTION OF PAPER AND CARDBOARD DESCRIPTION OF THE INVENTION The present invention relates to crosslinked polymers, based on the chemistry of polyamide, and its use in the paper and board industry to improve dry strength. A large amount of waste paper and cardboard was recycled, providing a source of cellulose fiber raw material for the paper. Residual paper, which has previously been treated with a wet-strength resin, is difficult to break in the pulping process and is therefore not a viable raw material for papermaking. On the other hand, the quality of the fiber in the waste paper deteriorates, due to the increasing recirculation, and the dry strength of a sheet of paper inevitably suffers as a consequence. There is now a desire to increase standards, associated with dry strength, closer to the values achieved with virgin fiber. The majority of paper manufacturing is now done under neutral pH conditions, is rated by the values between 6. 0 and 8.0 and new technologies must work efficiently under these conditions. Dry strength additives have been available in the paper industry for many years. Ref .: 193821 Natural polymers such as starch, either in their natural state or in their chemically modified form, have been used relatively successfully due to their abundance and low cost. There has been an attempt to add excessive amounts of starch because, although low in cost, the development of starch resistance, per dry kilogram per tonne of cellulose fiber, is between 5 and 10 times less than a synthetic polymer for dry strength. . Starch, even in its cationic form, has a low affinity for paper fibers and large amounts of solubilized materials remain in the water circuits of the paper forming machinery, where they act as nutrients for the bacteria and interfere with the affinity of other additives for papermaking. One of the first synthetic technologies to improve the dry strength of paper was based on acrylamide copolymers. Anionic versions of this chemical are many currently in use, usually combined with a cationic promoter, to aid in adsorption on paper fibers. The requirement of two chemical compounds, one of these may not contribute to the resistance is usually prohibitive in costs. The polyacrylamide technology was improved by adding reactivity to the aldehyde. Glyoxylated polyacrylamides were introduced to improve the resistance with the use of latent reactive aldehyde groups, which undergo internal crosslinking in the polymer during drying of the paper sheet at 80-100 ° C. The reactivity of the glyoxides difficult to control and the polymers continue to increase their viscosity during storage, reducing the shelf life. The reaction of the aldehyde is with specific pH and the development suffers above pH 6.5. If the reactivity of these polymers is very efficient, the wet strength of the treated paper is very strong and interferes with the repulping process. Polyamideamine polymers, in addition, react with epichlorohydrin, have been used successfully in the paper industry for several years as resins with wet strength. These additives are very reactive with pH values higher than 6.0 and temperatures higher than 802C. The crosslinking between the polymer chains is carried out inside the treated paper sheet, decreasing the solubility of the resin and preventing the formation of water with the interruption of the hydrogen bond of the internal fiber. It is clear that this chemistry also provides a high level of dry strength but this fact is usually irrelevant if the paper, in the form of a previous or later residue of the consumer, can not be repulped. The US 6 document, 056,967 and one of its priority applications, DE 196 21 300 Al, discloses the polyamide polymers obtained by the reaction products of alkylenediamines, polyalkylenepolyamines, ethylenically grafted polyamidoamines and the mixture thereof with crosslinking agents having at least two groups functional It has been found that certain crosslinked polyamides have excellent properties as a dry-resistant system for the production of paper and cardboard. The reaction of a di- or tri-amine with a di or tri-carboxylic acid produces a polyamide with a three-dimensional structure, which then reacts, to increase its molecular weight, with a di-tri-functional cross-linking compound. The increase in the mass of the three-dimensional structure is more efficient to join the spaces between the cellulosic fibers, allowing a greater number of hydrogen bonds that contributes to the bonding of internal fibers. The reaction of the polyamide polymer with the crosslinker is carefully controlled to remove any free reactive group in the final product, because this reactivity is known to contribute to the wet strength, which may cause undesirable cases. Solutions of the crosslinked polyamide polymer, which are dominantly cationic or anionic, depending on their desired construction, can be applied to an aqueous slurry of cellulosic fibers, sprayed onto a wet fibrous web or added to a partially partially dried sheet of a gluing press or movie press. The cationic polymer variants are self-retaining and their adsorption on cellulose fibers is independent of pH. This new technology also provides synergistic improvements in dry strength, when cationic and anionic polymer combinations are applied. The present invention seeks to employ all the advantages of polyamide chemistry, without the undesirable reactivity, associated with resins with wet strength. The three-dimensional polymers have a long shelf life, an active content of 20%, a pH of 6-7 and are free of antioxidants. Therefore, an object of the present invention is a cross-linked polymer formed by reaction between a polyamide (a) polymer backbone, with or without side chains, which is the product of the reaction of a primary di or tri-amine or mixtures of these, and a di-tri-or tetra-carboxylic acid or mixtures thereof, and a trifunctional crosslinking agent (b), based on the trichloro-, triepoxy- or trivinyl functional groups, or a cross-linking agent of formula (I 1 1 OO II II) C1H2CHCH2C - O - A - NC - - CN - A - O - CH, CHCH2C1 III \ OH HH OH where A is - (CH2) 2.6- and X is benzene or - (CH2) 2-6 -. The dominant charge of the polymer created by the reaction of (b) with (a) is cationic or anionic. The primary di- or tri-amine may possess secondary or tertiary amino groups within its structure. The di-primary amine is selected from diethylenetriamine, triethylenetetramine, tetraethylenepentamine, ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,6-hexanediamine, iminobispropylamine, N-methyl-bis- (to inopropyl) amine, bis- hexaethylenetriamine, 4,4'-methylenedianiline, 1,4-phenylenediamine or 4-aminophenyl sulfonate. 4,4'-methylenedianiline or diethylenetriamine is preferred.

The tri-primary amine is preferably tri (2-aminoethyl) amine. Also preferred OH O O H2N-A - NC-C- • CN-A-NH, I H H H I CN-A-NH, II O (") where A is - (CH2) 2-6 and X is benzene The molar ratio of di-tri-primary amine in the polyamide backbone polymer is 1: 0 a 0.5-0.5 Dicarboxylic acid is selected from oxalic, malonic, succinic, glutaric, adipic, pimelic, suberic, azelaic, sebasic, maleic, fumaric, itaconic, italic, isophthalic, terephthalic, and 1,4-cyclohexanedicarboxylic acids. Prefer the adipic or terephthalic acid, select the tri-carboxylic acid 1,2,3-benzenetricarboxylic acid, 1, 2,4-benzenetricarboxylic acid, 1,3,5-benzenetricarboxylic acid, nitrilotriacetic acid or N- (2-hydroxyethyl) - Ethylenediamine triacetic acid, 1,2,4-benzenetricarboxylic acid or nitrotriacetic acid is preferred, and di- and tri-carboxylic acids can also be used in the form of their corresponding ester, halide or anhydride derivatives.The molar ratio of di- or tri- -carboxylic in the main chain polymer d The polyamide is 1: 0 to 0.5: 0.5 at the molar ratio of carboxylic acid to the primary amine, for the preparation of the polyamide polymer, it is from 0.9: 1.0 to 1.0: 0.9. The polyamide polymer, with the internal secondary amine groups, can further be selected with benzyl chloride, propylene oxide, ethylene oxide, glycidol or a C-C ?8-succinic alkenyl anhydride, which forms a dominantly cationic polymer backbone with side chains. The polyamide polymer, with the internal secondary groups, can react more with acrylic acid, chloroacetic acid, glyoxylic acid or sodium salt of 3-chloro-2-hydroxy-l-propanesulfonic acid, in the presence of sodium or potassium hydroxide, which forms a predominantly anionic polymer backbone with a pH value > 6.0 The polyamide polymer, without groups of internal secondary amines, can further react with the glyoxylic acid in the presence of sodium or potassium hydroxide, forming a nonionic polymer backbone with anionic side chains. The molar ratio of the main chain of the polymer to the component of the secondary chain is 1: 0 to 1: 0.7. The tri-functional crosslinking compound (b) can be selected from tris- (3-chloro-2-hydroxypropyl) -2-hydroxy-propanol, tris- (3-chloro-2-hydroxypropyl) -sorbitol, tris- (3-) chloro-2-hydroxypropyl) -1, 2, 3-propoxy-glycerol, glycerol propoxylate of triglycidyl ether, N, N-diglycidyl-4-glycidyloxyaniline, N, N- (3-chloro-2-hydroxypropyl) -4- (3-chloro-2-hydroxypropyl) -oxaniline, glycerol propoxylate triacrylate, trimethylolpropane triglycidyl ether, trimethylolpropane trimethylacrylate, triphenylolmethane triglycidyl ether and tris- (2,3-epoxypropyl) isocyanurate. N, N-diglycidyl-4-glycidyloxyaniline or glycerol propoxylate of triglycidyl ether are preferred. The crosslinked polyamide polymer is prepared using a ratio of (a) to (b), equivalent to 1: 0.05 to 1: 0.7, based on the dry weight of each component. Another object of the present invention is an aqueous preparation comprising the present crosslinked polymer, the use of the present crosslinked polymer, optionally in the form of the aqueous preparation, as an additive in the processing of cellulosic fibrous material, preferably as an additive in the production of non-woven paper. The present crosslinked polymer can also be used to improve dry strength and wet strength of paper or nonwovens. Another objective of the present invention is a process for making paper with improved dry strength, which comprises adding the present crosslinked polymer. The aqueous preparation of the present cross-linked polymer can be applied to the paper at a point where the paper is in the form of a cellulose fiber slurry, a wet cellulosic fiber fabric or a partially dry sheet. The aqueous preparation of the present cross-linked polymer, with a dominantly cationic main chain, can be added to the cellulosic fiber slurry with an additional level of 0.05 to 1.0% dry polymer by weight of dry fibers, more preferably 0.05 to 0.4%. The aqueous preparation of the present crosslinked polymer, with an anionic or nonionic chain, dominantly cationic, can be sprayed through fine nozzles on the surface of a wet cellulose fabric, with an addition level of 0.05 to 1.0% of the dry polymer on the dry fiber weight, more preferably 0.05 to 0.2%. The aqueous preparation of the present crosslinked polymer, with an anionic or nonionic, dominantly cationic main chain, can be applied to a partially dry paper sheet with a gluing press, or dosed film press, with an addition level of 0.05 to 1.0. % of dry polymer on the dry fiber weight, more preferably 0.05 to 0.15%. The aqueous preparation of the present cross-linked polymer, with a dominantly cationic main chain, is added to the cellulosic fiber slurry and then a second aqueous preparation of the present cross-linked polymer is sprayed, with a dominantly cationic charge through fine nozzles on the surface of the cell. wet cellulosic fabric or applied to the partially dried treated paper sheet in a sizing press or dosed film press.

The second crosslinked polymer can be formed with a dominantly anionic chain, a copolymer of acrylamide and acrylic acid or methacrylic acid, anionic guar, carboxymethylcellulose, or anionic phenolic resin. The cross-linked cationic polymer is applied with an additional level of 0.05 to 0.8% dry polymer over the weight of the dry fiber, more preferably 0.05 to 0.20% and the cross-linked anionic polymer is applied with an addition level of 0.05 to 0.7%. dry polymer on the weight of the dry fiber, more preferably 0.05 to 0.15%. The following examples will demonstrate the current invention in greater detail.

EXAMPLES Example 1 (Reference to the prior art) This example describes the manufacture of a polymer, using a two-dimensional polyamidoamine backbone, which is then crosslinked with a two-dimensional dichloro derivative. Diethylenetriamine (108 g) and water (25 g) was mixed in a reaction flask equipped with a stirrer, distillation column, temperature probe and inlet for an inert gas. Adipic acid (146 g) was then added with stirring. The mixture was gradually heated to 170 ° C, under a constant stream of nitrogen gas. The original water and the additional water of the reaction were started to distill around 1202C, and were collected in a receiving flask. Stirring was continued at 170 ° C for another 7 hours, until distillation ceased. The heating source was removed and the distillation device was refluxed. Water (330 g) was added, very slowly first, by diluting the polymer of the main chain and forming a stable 40% solution with low viscosity (yield 542 g), with a temperature of 70-75sC. The polymer of the main chain (542 g) was then diluted with water (450 g) and cross-linked in steps, over a period of 12 hours, throughout the gradual addition of epichlorohydrin (45 g in total). The crosslinking reaction was verified by measuring the viscosity of the polymer solution and when it reached a value of 150 mPas (Brookfield RVT, weight 3, speed 100 rpm), no further epichlorohydrin additions were made. The polymer solution was cooled to 40 ° C and the pH 6.0-6.5 was adjusted with 50% sulfuric acid (75 g). The yield (1496 g) was achieved by adding more water, resulting in a polymer solution with a solid content of 20%. Using the procedure in Comparative Example 1, different variations of cross-linked polymers were produced, using different raw materials and molar ratios. The sample preparations all ended with the same physical specifications; that is, 20% of the solids content, a pH value of 6.0-6.5 and a viscosity of 200-300 mPas (Brookfield RVT, weight 3, speed 100 rpm). A clear intention of the present invention is to provide finished polymer without free reactive crosslinker, ensuring a long shelf life, without increasing the viscosity, and minimizing the contribution of the polymers with dry strength with the wet strength of the sheet. paper. The Example preparations are summarized in the following table (Examples 1-15). Table 1: Examples 1-15, preparations The samples produced from Examples 1-15 were evaluated in a paper manufacturing laboratory to evaluate the performance of dry strength in a paper stack. A slurry of 2% pulp was prepared in a 25 liter laboratory disintegrator by adding 400 g of bleached hardwood fiber, 19.6 liters of drinking water and stirring for 20 minutes. 1 liter of fiber slurry was placed in a suitable vessel, with agitator, and the required amount of polymer for dry strength was added. Stirring was continued at 500 rpm for 60 seconds. They used in the tests the addition levels of 0.2 and 0.4% (dry polymer based on dry fiber weight) of the preparations of Example 1-16. 200 ml of the sample from the storage were taken and formed into a handmade sheet using a British Standard Sheet Forming Device. For each test, 4 handmade leaves were made, to obtain a significant average. The "control" sheets did not have the polymer for dry strength. After removing the moisture with a suction roller from the formed fabric, using two blotters, the sheets were then pressed on stainless steel plates at 4.0 bar for 4 minutes, placed in drying rings and dried at 100 ° C in an oven. for 30 minutes. After conditioning at 50% RH and 232C for a minimum period of 12 hours, the sheets were ready for the resistance evaluation, carried out in the following manner.

Resistance to bursting The sheets were subjected to the dry burst strength test (TAPPI standard T403 OM-91, Paper Resistance Resistance). The results were recorded as a burst index (= burst value in kPa, divided by the leaf resistance in grams per square meter).

Tensile strength The sheets were subjected to wet and dry tensile strength test, were evaluated using a Lloyd WRK5 Traction Test device. Three 15 mm wide strips were cut from each leaf sample. For the dry strength measurement, the strip was clamped in Lloyd WRK5 jaws and the tensile test was started.

For wet strength measurement, the strip was first immersed in deionized water for 60 seconds. The excess water was then removed and the wet strip was subjected to the method, described above. The results were recorded as a tensile index (= tensile value in Néwtones, divided by the weight of the leaf in grams per square meter).

Table 2; Examples 1-15 Results of the Application Test ^ O 15 Interpretation of the results The index values recorded during the evaluation of the preparations of examples are directly proportional to the strength of the paper sheet. The S highest values of the indices are attributed to the three-dimensional main chain polymers, which have been further polymerized using a trifunctional chemical compound. The preparations represent the prior art, such as comparative example 1, are clearly inferior to the present invention. The wet tensile values, as expected, were too low to adversely affect the recycling of the finished paper. It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention is that which is clear from the present description of the invention. twenty

Claims (9)

CLAIMS Having described the invention as above, the content of the following claims is claimed as property: S 1. Cross-linked polymer formed by reaction between a polyamide polymer backbone (a), with or without side chains, which is the product of the reaction of a di- or tri-primary amine or mixtures thereof, and a di- or tri- or tetracarboxylic acid or mixtures thereof, and an I < B > of trifunctional crosslinking (b), based on functional trichloro-, triepoxy- or trivinyl groups, or a cross-linking agent of formula (III)
1. O O
2. II II C1H2CHCH, C - O - A - NC - X - CN - A - O - CH2CHCH2C1 I I I! ? 5 OH H H OH characterized in that A is - (CH2) 2-6- and X is benzene or
3. - (CH2) 2-6- - 2. Crosslinked polymer according to claim 1, characterized in that the tri-primary amine is tris (2-aminoethyl) amine or 5 O O II H, N -A-NC-X- CN-A-NH, H H
4. H
5. CN-A-NH, O (0
6. OH
7. O O
8. (II) A is - (CH2) 2-6 and X is benzene. 3. Crosslinked polymer according to claim 1, characterized in that the di-carboxylic acid is adipic or terephthalic acid. 4. Crosslinked polymer according to claim 1, characterized in that the tricarboxylic acid is 1,2,4-benzenetricarboxylic or nitrilotriacetic acid. 5. Cross-linked polymer according to claim 1, characterized in that (b) is N, N-diglycidyl-4-glycidyloxyaniline or triglycidyl ether glycerol propoxylate. 6. Crosslinked polymer according to any one of claims 1 to 5, characterized in that the polyamide polymer, with internal secondary amino groups, is further reacted with benzyl chloride, propylene oxide, ethylene oxide, glycidol or an anhydride. C4-C18 succinic alkenyl, which forms a dominant chain of cationic polymer with secondary chains. Crosslinked polymer according to any of claims 1 to 5, characterized in that the polyamide polymer, with internal secondary amino groups, is further reacted with acrylic acid, chloroacetic acid, 1 (0) glyoxylic acid or sodium salt of the acid 3-Chloro-2-hydroxy-l-propanesulfonic acid, in the presence of sodium or potassium hydroxide, which forms a predominantly anionic polymer backbone with a pH value of > 6.0 Cross-linked polymer according to any of claims 1 to 5, characterized in that the polyamide polymer, with internal secondary amino groups, is further reacted with glyoxylic acid in the presence of sodium or potassium hydroxide, which forms a main chain of nonionic polymer with anionic side chains. 9. Aqueous preparation, characterized in that it comprises a crosslinked polymer according to any of the preceding claims. 10. Use of a crosslinked polymer according to claims 1 to 8, optionally in the form of an aqueous preparation according to claim 9, as an additive in the processing of the cellulosic fibrous material. Process for manufacturing paper with improved dry strength, characterized in that it comprises adding a crosslinked polymer according to claim 1 to 8 or an aqueous preparation in accordance with the claim
9. 9.