A creping aid based on polyamides containing methyl bis(3-Aminopropylamine)

Abstract: A creping aid comprising the reaction product of a polyamide of a dicarboxylic acid or of the ester of a dicarboxylic acid and methyl bis(3-aminopropylamine) with epichlorohydrin in a mole ratio of the polyamide to the epichlorohydrin between about 1:0.1 and about 1:0.33, and a composition comprising an aqueous solution of the creping aid.

Description: This invention relates to a creping aid for use in the manufacture of wet-laid paper products in which a web of cellulosic fibers is subjected to a creping process in order to give it desirable textural characteristics, such as softness and bulk. In the manufacture of certain wet-laid paper products, such as facial tissue, bathroom tissue, or paper towels, a cellulosic web is conventionally subjected to a creping process that involves adhering the web to a rotating creping cylinder, such as the apparatus known as a Yankee dryer, and then dislodging the adhered web with a doctor blade. The impact of the web against the doctor blade ruptures some of the fiber-to-fiber bonds within the web and causes the web to wrinkle or pucker, and gives it such desirable textural characteristics as softness and bulk. The severity of the creping action is dependent upon a number of factors that include the degree of adhesion between the web and the surface of the creping cylinder. Greater adhesion causes increased softness, although generally with some loss of strength. In order to increase adhesion, an adhesive creping aid is used to enhance any naturally occurring adhesion that the web may have due to its water-content, which will vary widely depending on the extent to which the web has been previously dried. Creping aids also may prevent wear of the dryer surface, provide lubrication between the doctor blade and the dryer surfaces, and reduce chemical corrosion, as well as controlling the extent of creping. In order to provide a degree of adhesion that is durable enough to withstand the mechanical forces under the conditions of heat and/or moisture at the doctor blade, it is desirable to apply to the surface of the creping cylinder or previously incorporate in the web a resin having some ability to thermoset, i.e., to lose solubility and fusibility by crosslinking. However, the thermosetting nature of the resin affects its ability to impart wet strength to paper. Some wet-strength resins can function concurrently as creping aids, and in grades of paper that require wet-strength, such as facial tissue, napkin stock, and toweling, their use as creping aids is acceptable. However, in non-wet-strength grades such as bathroom tissue, it is desirable to restrict the thermosetting ability of a creping resin, so as to provide a durable coating on the dryer while limiting the development of wet strength in the paper. Adhesive creping aids, in aqueous solution or dispersion, are usually sprayed onto the surface of the creping cylinder. Alternatively, the solution or dispersion can be added at the wet end of the paper machine, e.g., to the pulp before formation of the sheet, or by spraying a solution or dispersion onto the wet web. Spraying on the dryer surface will minimize the chance that a relatively highly thermosetting resin could transfer to the sheet during creping, to impart possibly undesired wet-strength to a non-wet-strength grade of paper. However, any corrosive ions present in a resin would be concentrated on the dryer surface by this technique. Conversely, adding resin at the wet end of the paper machine would increase the wet-strength development by the more reactive thermosetting resins, but by diluting any corrosive ions in the white water, it would minimize their concentration at the dryer surface. U.S. Patent 4,501,640 discloses a creping adhesive comprising an aqueous mixture of a polyvinyl alcohol and a water-soluble, thermosetting, cationic polyamide resin that is the reaction product of epichlorohydrin and a polyamide having secondary amine groups derived from a polyalkylene polyamine and a saturated aliphatic dibasic carboxylic acid containing from 3 to 10 carbon atoms. The patent states that the polyvinyl alcohol is necessary to avoid hardening of the resin by diluting it. The resins employed by this patent are thermosetting wet-strength resins, made with relatively high ratios of epichlorohydrin to amine groups in the base polyamide. If they are added at the wet end, they will impart wet strength. If they are sprayed on the dryer surface, they will carry a relatively high content of potentially corrosive chloride ion into the adhesive film. Canadian Patent 979,579 discloses a creping aid that is the reaction product of epichlorohydrin and a polyaminopolyamide containing secondary amine nitrogen atoms, such as adipic diethylenetriamine polyamide, that has been alkylated with an alkylating agent or with a combination of formaldehyde and formic acid. All of the resins it describes require the additional alkylation process step in their manufacture, and some of its versions have the disadvantage that some residual formic acid or formate ion is carried over to the final resin. Such resins, if sprayed on the dryer surface, would carry residual formate ion as a component of the dryer coating. U.S. Patent 3,311,594 discloses a wet-strength additive for paper comprising the water-soluble reaction product of epichlorohydrin and a polyamide prepared by reacting a polyamine having at least three amine groups of which at least one is tertiary, with a saturated aliphatic dibasic carboxylic acid containing from 3 to 10 carbon atoms. The reaction product is water soluble but becomes crosslinked and insoluble on drying. The operable polyamines disclosed include methyl bis(3-aminopropylamine), usually referred to as MBAPA. These thermosetting wet-strength resins are made using a ratio of about 0.8 to about 2.0 moles of epichlorohydrin per mole of amine in the polyamide, or preferably about 1.0 to about 1.7 moles of epichlorohydrin per mole of amine. These resins are stabilized for storage by treatment with hydrochloric acid to convert the epoxide functional groups to chlorohydrin groups, which are then dehydrohalogenated to epoxide by an alkali treatment before use. The resins of this patent are thus highly functionalized, effective wet-strength resins, containing substantial amounts of chloride ion under conditions of their intended use. They would impart substantial wet-strength to the sheet if added at the wet end of the paper machine, and could potentially contribute to corrosion problems if applied to a Yankee dryer surface by spraying. U.S. Patent 4,487,884 discloses an aqueous solution of a water-soluble, cationic thermosetting resin derived by reacting N-bis(amino-propyl)-methylamine with a saturated dicarboxylic acid component comprising oxalic acid to form a polyaminopolyamide containing tertiary amine groups, the mole ratio of N-bis(aminopropyl)-methylamine to the acid component being from about 0.9:1 to about 1.2:1 and then reacting the polyaminopolyamide, in aqueous solution with from about 1 mole to about 1.5 moles of epihalohydrin per mole of tertiary amine groups present in said polyaminopolyamide. This composition would impart substantial wet-strength to the paper. U.S. Patent 3,640,841 discloses the manufacture of paper using as an adhesion aid, a polyaminopolyamide made from an aromatic or aliphatic dicarboxylic acid and a polyalkylene polyamine with two primary amino groups and at least one amino group which is either secondary or tertiary. The resins of this patent are described as having substantially no effect on wet strength of the paper, and as being easily soluble in water. Although their lack of wet strength makes them usable by wet-end addition to grades where wet strength is not wanted, they thus lack the self-insolubilization that is desired for durability of the coating on the Yankee dryer. It is recognized that a need exists, that is not met by the known compositions, for a creping aid that does not contain undesirable residual chemicals and helps to produce paper with the right balance of strength, stretch ability, softness, and absorbency. According to the invention, a creping aid for use in the manufacture of wet-laid paper products is the reaction product of a polyamide of a dicarboxylic acid or of the ester of a dicarboxylic acid and methyl bis(3-aminopropyl)amine, with epichlorohydrin in a mole ratio of the polyamide or ester to the epichlorohydrin between about 1:0.1 and about 1:0.33. Preferably, the reaction is carried out in aqueous solution and, with the total concentration of the reactants preferably being from 10 to 50%. The reaction minimizes steps that might produce harmful residuals, and the reaction product provides a creping aid that yields a sheet of paper with the right balance of properties. The product of the invention also has the advantage that the structure and solubility of the dicarboxylic (sometimes referred to as dibasic) acid used can be selectively varied to meet specific creping needs. The creping aids of this invention preferably are produced using a mole ratio between about 1:0.20 and about 1:0.30. The dicarboxylic acids can include saturated and unsaturated aliphatic and aromatic dicarboxylic acids having 2 to about 12 carbon atoms, including by way of example, oxalic, malonic, succinic, glutaric, adipic, pimelic, suberic, azelaic, sebacic, maleic, fumaric, itaconic, phthalic, isophthalic and terephthalic acids. Adipic and glutaric acids are preferred, with adipic acid being most preferred. The esters of the aliphatic and aromatic dicarboxylic acids may be used, as well as combinations of such dicarboxylic acids and esters. The intrinsic viscosity of the precursor polyamide may range from 0.090-0.225 dl/g with a preferred range being 0.10-0.20 dl/g. It is most preferred to terminate the reaction of the polyamide with epichlorohydrin when the reaction mixture has reached a Gardner-Holdt viscosity between about "F" and about "L", at a solids content of about 30%. For storage and sale, the resins are preferably diluted with water to a solution containing 12.0%-30.0% total solids, with 24%-26% total solids being preferred. For use as creping aids on the paper machine, the resins may be diluted further as desired before addition or spray application. The Brookfield viscosity range is from about 20 to about 500 cps as measured at a total solids content of 25%, with a viscosity range of about 40 to about 90 cps being preferred. The general formulas representing the polyamide and resin used in this invention are: POLYAMIDE: R = 0-10 RESIN: in which R = 0 to 10 EXAMPLE 1 SYNTHESIS OF POLY(ADIPIC ACID-CO-METHYL BIS(3-AMINOPROPYLAMINE) -EPICHLOROHYDRIN RESIN Methyl bis(3-aminopropylamine) [MBAPA, 218.0g, 1.5 moles] was charged to the reaction vessel. Adipic acid (219.2g, 1.5 moles) was added over a period of about 30 minutes. This was accompanied by an exotherm of about 30-40°C. The temperature was raised to 170-171°C and held for three hours while the water from the polycondensation was removed. The polyamide was diluted with about 350 cc of water. The final solution had a total solids of 51.4% with intrinsic viscosity of 0.112 dl/g (1M NH₄Cl, 2%, 25°C). A portion of the above solution (149.2g, 51.4% solution, equivalent to 76.7g solids, 0.3 mole) was charged to the reaction vessel and adjusted to 29-30% solids if necessary. The pH was adjusted from 9.8 to 8.5 with 7.5g of 96.8% H₂SO₄. Epichlorohydrin (6.9g, 0.075 mole, mole % ratio, 0.25 to 1) was added and the temperature raised to 53-54°C, representing a mole percentage ratio of .25 to 1. The viscosity was monitored with Gardner-Holdt tubes. At Gardner-Holdt "H-I", the reaction was terminated by adding 98 cc of water and adjusting the pH to 3.8-4.0 using 96.8% H₂SO₄. In this particular case, the sample was divided into three parts and stabilized at pH 3.8, 3.5, and 3.0. The total solids were 25.4% and Brookfield viscosity determined to be 61 cps (#1 spindle, 60 rpm, 25°C). All of the resins were stable to gelation during storage at 90°C for three months. EXAMPLE 2 SYNTHESIS OF POLY(GLUTARIC ACID-CO-METHYL BIS(3-AMINOPROPYLAMINE)-EPICHLOROHYDRIN RESIN Methyl bis(3-aminopropylamine) [MBAPA, 218.0g, 1.5 moles] was charged to the reaction vessel. Glutaric acid (198.2 g, 1.5 moles) was added over a period of 25 minutes. An exotherm of approximately 40 minutes accompanied the addition. The temperature was raised to 170-171°C and held for one hour while the water of polycondensation was removed. The polyamide was diluted with 325 cc of water and cooled to room temperature. The total solids of the aqueous solution was 51.6% and the intrinsic viscosity of the polyamide was 0.103 dl/g (1 M NH₄Cl, 2%, 25°C). A portion of the above solution (140.4g, 51.6% solution, equivalent to 72.5g solids, 0.30 mole) was charged to the reaction vessel and adjusted to 29-30% solids if necessary. The pH was adjusted from 9.6 to 8.5 with 96.8% H₂SO₄. Epichlorohydrin (4.9g, 0.056 mole) was added and the temperature raised to 51-52°C. At Gardner-Holdt viscosity of "F-G" the reaction was terminated by adding 93 cc of water and adjusting the pH to 3.8-4.0 with 96.8% H₂SO₄. In this particular case, the resin was divided into three parts, and the pH adjusted to 4.0, 3.5, and 3.0. The total solids were 24% and Brookfield viscosity determined to be 40 cps (#1 spindle, 60 rpm, 25°C). All of the resins were stable to gelation during storage at 90°F for three months. EXAMPLE 3 SYNTHESIS OF POLY(AZELAIC ACID-CO-METHYL BIS(3-AMINOPROPYLAMINE)-EPICHLOROHYDRIN RESIN Methyl bis(3-amino propylamine)[MBAPA, 218.0g, 1.5 moles] was charged to the reaction vessel. Azelaic acid (282.3 g, 1.5 moles) was charged to the reactor over a period of about 40 minutes. An exotherm of approximately 20°C accompanied the addition. The temperature was raised to 170°C and held for the three hours while the water from the polycondensation was removed. The polyamide was isolated by pouring the contents of the reactor into an aluminum pan and allowed to cool. The intrinsic viscosity was determined to be 0.106 dl/g (1MNH₄Cl, 2%, 25°C). A portion of the polyamide (59.5g, 0.20 mole) prepared above was dissolved in 144 cc of water containing 6.0g of 96.8% H₂So₄. Epichlorohydrin (4.6, 0.05 mole, mole % ratio, 0.25 to 1) was added, and the temperature raised to 55-58°C. At Gardner-Holdt viscosity "F-G", the reaction was terminated by adding 72 cc of water and adjusting the pH to 3.9 with 96.8% H₂SO₄. The total solids of the final resin were 25.1% and the Brookfield viscosity determined to be 55 cps (#1 spindle, 60 rpm, 25°C). The resin was storage-stable for more than three months. The Example was repeated with a mole % ratio of epichlorohydrin to polyamide of 0.175 to 1 (30% less). EVALUATION PROCEDURE The resins were evaluated as creping adhesives using the method described in U.S. Patent 4,501,640 (D.A. Soerens). Kymene® 557 was cited as a control for the work described in the that patent. The evaluations of the creping aids according to the invention included Kymene® 557 and Creptrol® 190 as resin controls. (Kymene 557 resin is a wet-strength resin and Crepetrol 190 is a creping adhesive resin, both commercially available from Hercules Incorporated). PREPARATION OF SAMPLES FOR THE MODIFIED 180° PEEL TEST 1. Clean 5.08 cm (2") x 12.7 cm (5") x 1.6mm (1/16") stainless steel plates with soap and water, dry, wipe with hexane, and dry. 2. Cast a film of the creping aid resin on to 901.6 ≈4" of the stainless steel plate with a #26 wire wound rod. Allow film to dry overnight. 3. Place coated stainless steel plate on a hot plate set at 93.3°C (200°F) for five minutes. 4. Soak a 1" x 8" cotton cloth strip of about 108.50 gm/m² material (i.e. ≈3.20 oz./yd²) for 60 seconds in distilled water and hold upright to drain off excess water for ≈60 seconds. 5. Place the wet cotton strip on the coated stainless steel plate on the hot plate and roll with a 1000g roller to laminate cloth to the film. 6. Allow laminate to dry for two minutes on the hot plate after rolling. 7. Submit samples for modified 180° Peel Test at 99°C with a crosshead speed equal to 15.2 cm/min. (6"/minute). N.B. A.S.T.M. Test D-903 was used as a guide with modifications as follows: a 2.5 cm (1") sample vs. a 50.8 mm (2") sample and the crosshead speed set at 15.2 cm/min. (6"/min) vs. 30.5 cm/min. vs. (12"/min). Comparative test results of Examples 1 and 3 are listed in Table 1, using Crepetrol • and Kymene • as controls for comparison. The data in the table demonstrates that the samples of the current invention compare quite well to the controls Crepetrol® 190 and Kymene® 557H. Designation Sample Average Peel Strength N/cm (lbs./in.) Peak Peel Strength N/cm (lbs./in.) Control Crepetrol® 190 0.14 (0.08) 0.228 (0.13) Example 1 Adipic acid-MBAPA 0.14 (0.08 0.245 (0.14) Example 3 Azelaic acid-MBAPA 0.123 (0.07 0.227 (0.13) Low Epi Azelaic acid-MBAPA 0.227 (0.13 0.403 (0.23) Control Kymene® 557H 0.245 (0.14 0.700 (0.40) Polymer Designation Observations Poly(adipic acid-co-MBAPA) Starting Copolymer of invention Soluble in H₂O Poly(adipic acid-co-MBAPA)-epi Copolymer of invention Gel particles, some solubility Poly(adipic acid-co-MBAPA)-epi Copolymer of U.S Patent 3,311,594 Swelled gel formation Poly(adipic acid-co-Diethylenetriamine) Starting Copolymer of Crepetrol® 190 Soluble in H₂O Crepetrol® 190 Creping aid of Can. Pat. 979,579 Swelled gel formation Kymene® 557H Wet-strength resin Swelled gel formation

Claims: A creping aid for use in the manufacture of wet-laid paper products is the reaction product of a polyamide of a dicarboxylic acid or of the ester of a dicarboxylic acid and methyl bis(3-aminopropyl)amine, with epichlorohydrin in a mole ratio of the polyamide to the epichlorohydrin between 1:0.1 and 1:0.33. A creping aid as claimed in claim 1, further characterized in that the mole ratio is between 1:0.20 and 1:0.30. A creping aid as claimed in claim 1 or 2, further characterized in that the reaction product is obtained by a reaction with the total concentration of the reactants being from 10 to 50%. A creping aid as claimed in claim 1, 2, or 3, further characterized in that the dicarboxylic acid is selected from the group consisting of oxalic, malonic, succinic, glutaric, adipic, pimelic, suberic, azelaic, sebacic, maleic, fumaric, itaconic, phthalic, isophthalic and terephthalic acids, and the esters of the said dicarboxylic acids. A creping aid as claimed in claim 4, further characterized in that the dicarboxylic acid is adipic or glutaric acid. A creping aid as claimed in claim 3, further characterized in that the dicarboxylic acid is adipic acid. A creping aid as claimed in claim 1, in which the polyamide has an intrinsic viscosity in the range of from 0.090 to 0.225 dl/g. A creping aid as claimed in claim 6, in which the polyamide has an intrinsic viscosity in the range of from 0.10 to 0.20 dl/g. A composition of matter comprising an aqueous solution of the creping aid as claimed in claim 1 containing 12 to 30% of the creping aid. Process for preparing a creping aid for use in the manufacture of wet-laid paper products comprising reacting a polyamide prepared by reacting a dicarboxylic acid or an ester of a dicarboxylic acid with methyl bis(3-aminopropyl) amine, with epichlorohydrin in a mole ratio of the polyamide to the epichlorohydrin between 1:0.1 and 1:0.33.

Inventors: ESPY HERBERT HASTINGS, MASLANKA WILLIAM WALTER, ESPY, HERBERT HASTINGS, MASLANKA, WILLIAM WALTER
Applicants: HERCULES INC, HERCULES INCORPORATED
Application year: 1992
Main classification: D21H21
IPC codes: D21H17, D21H27, C08G69, D21H21