JPH0223575B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to polyvinyl alcohol, and more particularly to stable aqueous polyvinyl alcohol/melamine-formaldehyde resin complex compositions. Currently, a number of commercially available wet end additives are used in paper production. These have many limitations. Examples of some of the most commonly used additives are: Cationic starches are used to improve the retention of cellulosic fibers, fillers and pigments, and are also often used to increase the dry strength of finished papers. However, such improvements are generally modest and, at the same time, the use of cationic starches increases the risk of operational irregularities (batch irreproducibility, low solution stability, low wet strength), other compatibility with ingredients (alum, size, other salts) and leading to high biological oxygen demand (BOD) for additives that are not on the pulp or are recycled and are lost in the wastewater. obtain. Cationic urea-formaldehyde UF resin,
Amine-containing polyamides treated with epoxides (e.g. Hercules'"Kymene" 557) or melamine-containing
Other wet end additives such as formaldehyde (MF) resins (eg, American Cyanamid's "Parez" 607) are also often used to impart permanent wet strength to the resulting paper. However, UF resins are slow to vulcanize on machines, while polyamides are relatively expensive and slow to adsorb onto cellulose pulp.
Makes paper relatively difficult to repulp.
MF resins have poor pigment and filler retention and also exhibit low water absorption, although absorption is often desired as well as wet strength. All of these types of additives provide only modest increases in dry strength. The above types are now being used as wet film strength improvers (at their normal working concentrations) to allow a higher degree of production control and in some cases increased productivity. None are approved. Conventional soluble polyvinyl alcohol in the form of powder, granules or chopped fibers has been used as an additive in the wet end of paper making machines in Japan. Increased paper strength and oil resistance was disclosed. However, careful control of the particle size of the polyvinyl alcohol, the preliminary heat treatment and the degree of hydrolysis of the polyvinyl alcohol is required. At the same time, careful control of the temperature and level of water absorption by the particles and the forming paper is required before passing through the dryer rolls (CA
Edited by Tinch “Polyvinyl Alcohol”
Wiley, N. Y. (1973) 301-305
(see page). Since these particles are non-ionic, they would be expected to have poor fiber retention, and since they are non-vulcanizable, they have no wet strength capabilities. The use of melamine-formaldehyde resins as wet end additives to obtain papers with high wet strength is known (C. in TAPPI Book No. 29).
S. Maxwell's review article "Wet Strength in Paper"
and Paperboard”, edited by J.P. Weidner (1965) 20
(See pages 32 to 32). The interaction of starch and cationic precondensates of melamine-formaldehyde to form cationic starch (facilitating binder adsorption) is disclosed in US Pat. No. 2,998,344 (see paragraph 3). No concentration effects were noted to be significant. Also, the product was not satisfactory in itself as a binder for cellulosic pulp (see paragraph 6). U.S. Pat. No. 3,594,271 describes a cationic thermosetting melamine-formaldehyde acid colloid and its
An aqueous acidic colloidal solution of a cationic reaction product with 50 to 50 times its weight of water-soluble starch and a method for treating paper using the same are disclosed. Such products are disclosed to provide good adsorption onto fibers and increased dry strength with low wet strength. The total solids content of the mixture is between 2 and 10%, but it is indicated that "this is not critical" (paragraph 2). It was also disclosed that the low wet strength was the result of a low concentration of melamine-formaldehyde resin relative to starch. U.S. Patent No. 3,424,650 discloses that formaldehyde
It was disclosed that starch reacted with guanidine-melamine resin had much increased adsorption to cellulose fibers. 9 to 14/0.4 to 1.6/0.4 respectively using all three materials as reactants
1.6 in order to produce a relatively stable resin and to obtain sufficient activity to increase the dry strength of paper articles by prior reaction with starch. was important.
The concentration of reactants can also be between 1 and 40% by weight. U.S. Pat. No. 3,002,881 describes a formulation of about 2/1 weight ratio of guanidine-formaldehyde resin and hydrocolloid (such as starch or polyvinyl alcohol) as a good wet end additive to increase the wet strength of the resulting paper. has been disclosed. Presumably, the ingredients are added independently to the dilute pulp slurry. Due to the lack of stability of the premix, there is no indication of prereaction of the resin and polyvinyl alcohol (see stage 5). The advantages of using cationic materials (cationic starches) in the wet end of paper machines are disclosed in US Pat. No. 4,029,885. Other methods of making cationic highly adsorbed polyvinyl alcohols have also been described. However, these tend to be more costly and/or pose problems with toxic reactants. These are: US Pat. Nos. 3,597,313 and 3,772,402 disclose copolymers of vinyl alcohol modified with cationic monomers. US Pat. No. 3,051,691 discloses that polyvinyl alcohol and calcium cyanamide form a cationic polymer polyol that dyes directly against cellulose. United Kingdom patent for use of polyvinyl alcohol and methylolmelamine (monomeric melamine-formaldehyde) in paper coatings
Described in No. 551950. Application as a textile finish is disclosed in US Pat. No. 2,876,136.
In the latter, the reaction between the two components likely did not occur until after application to the substrate (the catalyst was added at this point). The disclosed polyvinyl alcohol/methylol compound ratio was from 1/1 to 1/125. US Pat. No. 3,067,160 disclosed that even small amounts of polyvinyl alcohol were unsuccessfully added to cationic melamine-formaldehyde resin acid colloids (in the methyl ether form). Such systems are very unstable and undergo gelation, and therefore stable melamine containing polyvinyl alcohol
Formaldehyde acid colloidal solutions show no promise. It has long been known that addition of crosslinking agents at moderate to high concentrations of polyvinyl alcohol in aqueous solution leads to gel formation, but if this solution is sufficiently dilute, intermolecular interactions occur almost exclusively; No gel will form at all (W. Kuhn and G.
Balmer, Journal of Polymer Science Volume 57
(See pages 311-319 (1962)). Furthermore, the work of these authors has shown that the reaction of polyvinyl alcohol with a degree of polymerization on the order of 1000 to 2000 with highly functional crosslinking agents such as melamine-formaldehyde resin acid colloids (and the latter containing as much as 20 to 100% by weight of PVA) This indicates that at high concentrations (approximately 0.3-0.5%), very low concentrations of PVA must be present to prevent gelation. Thus, the interaction (complexation) of PVA and MF resin acid colloids can occur at solution concentrations as high as 3.75%, giving a stable but still active system even with extensive heating of the solution. is astounding. These authors show that complete separation of the polymer chains is necessary for this dilution effect to occur. Other researchers have also shown that complete separation of polyvinyl alcohol molecules requires concentrations below 0.25%, and that if the concentration increases to about 0.9%, the swollen polymer coils must penetrate. [See JGPritchard, Gorden and Breach, "Polyvinyl Alcohol," NYD, (1979), p. 15]. In accordance with the present invention, a complex of a polyvinyl alcohol polymer and a cationic melamine-formaldehyde resin acid colloid in a polyvinyl alcohol/melamine-formaldehyde resin acid colloid weight ratio of about 1/1 to about 5/1 on a dry weight basis;
Approximately 0.7% by weight to a level that does not cause gelation to the point where there is no flow under the force of gravity (6)
polyvinyl alcohol/melamine, consisting of sufficient water to give a solids content of not more than % by weight.
Stable aqueous compositions of formaldehyde resin complexes are provided. Further in accordance with the present invention there is provided a method for making stable aqueous compositions of the polyvinyl alcohol/melamine-formaldehyde resin complexes of the present invention. The term "stable" as used herein means that gelation to the point of no flow under the force of gravity does not occur within 48 hours. Contrary to the indications of the prior art cited above, and quite surprisingly, formulations of polyvinyl alcohol and cationic melamine-formaldehyde resin acid colloids do not work at concentrations as high as about 3% or at temperatures up to 85-90°C. We have discovered that it is possible to interact in solutions of even higher concentrations for 1 to 2 hours, if desired, without leading to visible levels of gel or without losing the adsorption activity of the complex on cellulose. . With this discovery,
Polyvinyl alcohol/melamine-formaldehyde as these concentrations and reaction rates allow equipment already used for solutions of cationic starch added to paper machines to obtain improved properties. The interaction will be commercially compatible. The limitations of prior art wet end additives discussed above are reflected in the polyvinyl alcohol/melamine-
Reduced by the use of formaldehyde resin complexes. Improvements over cationic starches include improved batch reproducibility, higher solution stability, higher wet film strength, and better compatibility with other components in the feed (salts, size, fillers) of the paper produced. exhibited by lower BOD (biological oxygen demand), higher fiber retention and higher dry strength, dry strength and wet strength and toughness. For wet strength agents, the improvement over urea/formaldehyde resins is shown in high on-machine vulcanization rates. Advantages over melamine-formaldehyde resins include higher water absorption rates of the resulting paper (in unsized compositions);
It exhibits higher fiber retention and higher wet strength. The advantages over nonionic polyvinyl alcohols as wetting additives are easier process control, better fiber retention, and better sheet properties, including paper wet strength capabilities, using other cationic polyvinyl alcohols. The above improvements are demonstrated by the wet strength capabilities and process advantages described above. Thus, there is provided the production of certain complexes of polyvinyl alcohol and cationic melamine-formaldehyde resin acid colloids that are highly adsorbent to cellulose pulp, and as such are of great interest for applications in the paper industry. suitable.
These complexes can be dried to form water-resistant products, but also still exhibit good solution stability at solution concentrations up to about 3.75% by weight or even higher. These complexes can be manufactured more easily and at a lower cost to the customer than the highly adsorbent polyvinyl alcohols previously described. However, these require fairly specific conditions for their manufacture in order to obtain a product with more advanced properties than other wet end additives to the manufacturing process. The enhanced properties of good solution stability, high adsorption capacity on cellulose pulp, enhanced processability and control and improved paper quality make the complexes of the invention particularly suitable for use in the wet end of paper machines. It becomes suitable,
Also, the overall cost of the paper mill can be reduced. The polyvinyl alcohol polymer component of the complexes of the present invention can be of a "fully" hydrolyzed grade (hydrolysis mole percent of acetate groups from 99.0 to about 100%), a partially hydrolyzed grade (hydrolysis percentage of 80 to about 100%), 90%),
It can be a polymer or formulation of intermediate levels of hydrolysis. When paper with the highest wet strength properties is desired, fully hydrolyzed grades and even higher molecular weight commercial grades are preferred. The polyvinyl alcohol shall have a degree of polymerization of about 600 to about 3000, as reflected by an intrinsic viscosity (πinh) of about 0.3 to about 1.4 dl/g. Intrinsic viscosity in water at 30℃
Measure at a concentration of 0.5 g/dl. This is approximately
For many commercial grades of polyvinyl alcohol, solution viscosities of about 4 to about 160 CPS (4%
Aqueous solution, at 20° C., corresponds to Hoeppler's falling ball method, but about 10 to 70 centipoise is preferred. The polyvinyl alcohol component of the present invention can also be a copolymer of vinyl alcohol, such as one obtained by hydrolyzing a copolymer of vinyl acetate and small amounts (up to about 15 mole percent) of other monomers. Suitable monomers are, for example, esters of acrylic acid, methacrylic acid, maleic acid or fumaric acid, itaconic acid and the like. Copolymerization of vinyl acetate with hydrocarbons such as α-olefins such as ethylene, propylene or octadecene, vinyl butyrate, 2-
Copolymerization with higher molecular weight vinyl esters such as ethylhexoate, stearate, trimethyl acetate, or homologues of these (Shell
Vinyl esters of the type "VV-10" sold by Chem.Co.) are hydrolyzed to give copolymers which can be suitable polyvinyl alcohol polymers.
Other suitable comonomers are N-substituted acrylamide, vinyl fluoride, allyl acetate, allyl alcohol, and the like. Free unsaturated acids such as acrylic acid, methacrylic acid, monomethyl maleate, etc. can also act as comonomers, although the stability of the final product (ie, after reaction with the melamine-formaldehyde resin) is reduced. The other key ingredient, the cationic melamine-formaldehyde resin acid colloid, is trimethylolmelamine (TMM) (or American
Slightly polymerized TMM with certain feeds added to facilitate dissolution in water, such as Cyanamid Corporation's product "Parez" 607) in water containing hydrochloric acid (approximately 0.8 moles per mole of TMM). HCl)
Low molecular weight polymers (MW approx.
1700) as a colloidal solution. These colloidal particles are positively charged (cationic) and are known to irreversibly adsorb onto negatively charged cellulose fibers even at very low concentrations. These are called "regular" colloids. A detailed discussion on melamine-formaldehyde resin acid colloids can be found in TAPPI Book Series No. 29
"Wet Strength in Paper and Paperboard"
(ed. by John Weidner Tech, Assoc. of the Pulp
and Paper Industry, NYC, (1965), 20–
(page 32). Included in this discussion, and also preferred for use in the complexes of the invention, are so-called "high efficiency" melamine colloids, in which an excess of formaldehyde of 1 to 7 moles per mole of TMM is added to the TMM. In addition, the optimal HCl/TMM molar ratio is reduced from about 0.8 to about 0.6. In order to maximize efficiency, "high efficiency" is required.
A colloid of is preferred. The inventors believe that "highly efficient"
It has also been found that when melamine-formaldehyde colloids are prepared by dissolving TMM in cold water followed by addition of acid, there are some benefits to the final paper quality. The preparation of the melamine-formaldehyde component by this "cold" procedure is described below. To avoid poor solubility and binding properties,
Polyvinyl alcohol must not be present in the solution during the preparation of the melamine-formaldehyde resin acid colloid. In the production of "high efficiency" type cationic melamine formaldehyde resin acid colloids, aldehydes other than formaldehyde can be added during the colloid ripening process. These aldehydes can contain up to about 10 carbon atoms. The concentration is 8 to 8 based on the weight of trimethylolmelamine.
It can be 100% by weight. The types of aldehydes that may be used include simple homologs of formaldehyde, including branched-chain versions. Examples are acetaldehyde, propionaldehyde, butyraldehyde or 2-ethylhexylaldehyde. Acetaldehyde is particularly effective, especially at low concentrations (see Example 14). Phenylacetaldehyde, chloroacetaldehyde, 3
-Substituted aldehydes such as methoxypropionaldehyde, aldol and crotonaldehyde are also useful. Polyaldehydes that may be used include glutaraldehyde, glyoxal, adipaldehyde and terephthalaldehyde. Glutaraldehyde is particularly useful for obtaining unusually high filler retention, Scott internal bond strength and wet tensile energy adsorption values (see Example 15). When adding polymeric aldehydes, the optimum
The HCl/TMM molar ratio is closer to 0.8 than 0.6. Other ingredients may also be present during the reaction of the polyvinyl alcohol and melamine-formaldehyde resin acid colloid, provided they can act as diluents to reduce cost while not reducing certain properties such as pigment retention. These things include
Included are unmodified starches, low grade (acid modified, enzyme converted) starches, modified starches such as hypochlorite oxidized starch, or starch derivatives such as hydroxyethyl starch or cationic starches. The amount of starch that can be added may vary, for example to produce a 6/1/1 starch/polyvinyl alcohol/melamine formaldehyde complex and still obtain some improvement over the use of a starch/melamine-formaldehyde complex. Approximately 6 parts by weight
Larger parts by weight of the above starches may be used. For example, see Tables XI and XII of Example 13, where the advantages of 3/1/1 starch/polyvinyl alcohol/melamine-formaldehyde are shown over 3/1 starch/melamine-formaldehyde. The polyvinyl alcohol/melamine-formaldehyde resin ratio can be from about 1/1 to about 5/1 by weight on a dry basis. Increasing the ratio reduces the adsorption level on the pipe. On the other hand, too low a ratio leads to a brittle product, which is reflected in the reduced physical properties of the paper produced. Polyvinyl alcohol and melamine-formaldehyde resin acid colloids can be prepared by mixing aqueous solutions of each at room temperature for several hours or by heating (30° to 90°C, about 3 to about 15 minutes), or by preparing polyvinyl alcohol powder or granules. The interaction can be achieved by slurrying the agent in a melamine-formaldehyde acid colloid followed by heating and stirring at about 80 DEG to 95 DEG C. until the polyvinyl alcohol is dissolved. However, in all variants, the total solids concentration after mixing is approximately
It is important that concentrations range from 0.7 to about 3.75% by weight or even higher to levels that do not cause gelation to the point of no flow under the force of gravity, but not exceeding 6% by weight. At higher concentrations, the viscosity of the mixture increases more rapidly than is likely useful, causing gel formation. At a solids concentration of 8%, gelation can occur in a few minutes, but at a concentration of 5%, gelation may occur after about 48 hours or not, depending on how favorable other conditions are. There is no such thing. Preferably, the total solids concentration is about 2% to 3% by weight.
It should be between. One of the most economical methods for producing the complex is as follows. Trimethylolmelamine is dissolved in water and hydrochloric acid at room temperature in an acid-resistant tank and aged to form an oligomer. This is then pumped into another tank (the interaction tank) where it is diluted with water to a concentration of approximately 0.6% by weight. In the third tank, the polyvinyl alcohol is dissolved with heat and stirring to a 10% by weight solution. The latter is then pumped hot into a complexing vessel (containing a melamine-formaldehyde resin acid colloid) and the mixture is slightly agitated to form the final product. Preferably, a polyvinyl alcohol/melamine-formaldehyde ratio of about 2/1 to 3/1 and a total solids concentration of about 2% by weight are used.
The temperature of the reaction mixture is then about 33°C, which is high enough to ensure the formation of the complex within a mixing time of about 15 minutes. If a mixing time of about 24 hours is allowed, the mixing temperature can be room temperature (about 20°C). An alternative route to complexes such as those described above is to add powdered polyvinyl alcohol directly to diluted melamine-formaldehyde resin acid colloid to form a slurry in a complexing bath and then for 0.25 hours to 2 hours.
and heating to about 85-90° C. for an hour or until the polyvinyl alcohol dissolves. The advantage of this route is that the dissolution of polyvinyl alcohol is rapid in such a medium (approximately 15 minutes) and does not require a third bath. The disadvantage of the latter method is that it requires more energy to heat the larger volume of solution. The aqueous composition of the complex obtained from both procedures is
Stable on storage for at least 3 weeks (viscosity,
regarding activity). In some cases, we observed no change in solution viscosity for more than 3 months. A formulation of a solid polyvinyl alcohol melamine in the form of a powder or granules with a solid, water-soluble or aqueous acid-soluble condensation product of 3 moles of formaldehyde is also applicable, e.g. to a slurry procedure. It can be used in some cases. The dry formulation is added, preferably cold, to water or, if desired, an aqueous acid and formaldehyde added thereto to dissolve the melamine-formaldehyde condensation products and convert them into cationic resin acid colloids. , the polyvinyl alcohol can remain in substantially insoluble form as a slurry. An appropriate amount of water is then added to give a final solution containing about 0.7% to about 6% solids, and the slurry is heated as before to dissolve and react the polyvinyl alcohol. Polyvinyl alcohol/
The ratio of melamine-formaldehyde resin acid colloid can be from about 5/1 to about 1/1 by weight. The polyvinyl alcohol used must have as low a cold water solubility as possible, approximately 8
Grades with a maximum cold water solubles content of % by weight can be used, while grades with a maximum of about 4.5% by weight are preferred. A maximum cold water solubles content of about 2% by weight is most desirable. Melamine-formaldehyde resin acid colloids should be prepared under milder conditions than the previous procedure, including using higher degrees of dilution to prevent gelation, and typically contain 14 to 18% solids by weight. A concentration of 9% by weight rather than a concentration of 9% by weight gave better results. The structure of the polyvinyl alcohol/melamine-formaldehyde complex of the present invention has not been determined in detail. However, the infrared spectrum of the cast film forms a graft copolymer of polyvinyl alcohol and melamine-formaldehyde resin. The chemical interaction through -OH group is shown. The polyvinyl alcohol/melamine-formaldehyde complex is preferably used using conventional methods for producing paper sheets and other cellulosic products. Preferably, the interaction with the cellulose pulp material is effected by adding it internally to the cellulose pulp prior to forming the paper sheet. The aqueous solution of the complex is thus added to the aqueous suspension of the paper stock, which is then fed into the Fourdrinier head box.
It can be added at any point in the process prior to the fan pump, feed container, hydropulper, or other point of sheet production. The high rate of adsorption of polyvinyl alcohol/melamine-formaldehyde complexes to pulp allows many alternatives in this context. Among the wide variety of pipes that can be effectively processed are bleached and unbleached sulfate (kraft), bleached and unbleached sulfite, soda, neutral sulfite, semi-chemical products, powdered materials or blends of these fibers. There is. Additionally, fibers of viscose rayon, glass, regenerated cellulose, polyamide, polyester or polyvinyl alcohol may also be used in conjunction with cellulose pulp. The preferred PH range for pulp stocks containing polyvinyl alcohol/melamine-formaldehyde complexes is from about 5 to about 8, with good adsorption and filler retention shown over this range. The best wet strength properties of the resulting paper occur within the PH range of about 4 to about 6.5. Materials that can be added to the pulp slurry along with the polyvinyl alcohol/melamine-formaldehyde complex include cationic surfactants, cationic urea-formaldehyde resins, or cationic polyacrylamide. Polymers derived from polyamides containing amino groups along the backbone of the polymer and also reacted with epichlorohydrin (such as "Kymere" 557 from Hercules) can also be added. Anionic polyacrylamide polymers, reinforced rosin sizes, fillers, pigments, alum, etc. may also be present. The sheet is then formed, compressed, and dried in the conventional manner. The later stage is polyvinyl alcohol/
It serves to preserve the melamine-formaldehyde complex in a water-insensitive state. Good runnability and good paper formation were demonstrated. Polyvinyl alcohol added to pulp slurry/
The amount of melamine-formaldehyde complex ranges from about 0.02 to about 10% based on the dry weight of the pulp. The preferred range is about 0.05% to 3%, which provides the desired properties in a finished paper product.
Depends on pulp type and specific operating conditions. Thus, polyvinyl alcohol/melamine
If the formaldehyde is too small in the slurry,
Only very small improvements in the properties of interest can be obtained. Too expensive polyvinyl alcohol/melamine-formaldehyde can be uneconomical. The following examples are intended to illustrate the invention. All parts, percentages and proportions are by weight unless otherwise indicated. Reference Example of Production of Melamine-Formaldehyde Resin Acid Colloid A "High efficiency" melamine-formaldehyde resin acid colloid was mixed with 13.2 g of concentrated reagent-grade hydrochloric acid in distilled water.
It was prepared by adding 365 g. Next, 50 g of trimethylolmelamine powder was added while stirring, followed by 95 g of a 37% formaldehyde aqueous solution. After stirring gently overnight at room temperature, a blue hazy state clearly appeared as expected. Dilute this acid colloid with 365g of distilled water to 7.4%
Solid (determined by drying in an air circulation oven at 110° C./1 hour). This is about 74% of theory if no formaldehyde was lost during the drying process. From the first ratio above, per cell of trimethylolmelamine
0.6 mole HCl and trimethylolmelamine 1
5 moles of formaldehyde are obtained per mole. When a drop of concentrated hydrochloric acid was added to a few ml of the acid colloid, coagulation occurred immediately, as would be expected if the melamine-formaldehyde acid colloid had been sufficiently aged. The pH of the colloid was 1.8.
Acid colloid stability was excellent for at least one month. Reference Example B An alternative method for producing melamine-formaldehyde resin acid colloids is as follows. Reagent grade concentrated hydrochloric acid (11.6 g) was added to 346 g of distilled water. Then, with stirring, 43.2 g of commercially available spray-dried trimethylolmelamine ("Parez" 607 from American Cyanamid Corporation) was added. The solution was gently stirred at room temperature overnight. The acid colloid was diluted with 346 g of distilled water to form a 5.70% solids colloidal dispersion. The molar ratio HCl/TMM was 0.6/1.0. Reference Example C Another alternative method for producing melamine-formaldehyde resin acid colloid is shown below. Reagent grade concentrated hydrochloric acid (15.8 g) was added to 390 g of distilled water. Next, 43.2 g of "Parez" 607 was slowly added while stirring.
The solution was then stirred at room temperature overnight. This acid colloid was diluted with 340 g of distilled water to form a 6.6% solids colloid dispersion. Molar ratio HCl/TMM is 0.8/1.0
It was hot. Reference Example D A "cold" procedure for producing melamine-formaldehyde resin acid colloids is shown below. The component ratio is the same as Reference Example A. Add trimethylolmelamine to 150g of distilled water cooled to 140℃ on ice.
25g was added with stirring. Next, 47.5 g of 37% formaldehyde was added, and 32.5 g of distilled water was added to this suspension.
6.6g of concentrated hydrochloric acid was added. After stirring for several hours,
The suspension became a milky solution. The temperature was allowed to rise at room temperature overnight with gentle stirring and diluted with 182 g of distilled water. The percentage of solids was 6.9%. Manufacturing Example 1 of Polyvinyl Alcohol/Melamine-Formaldehyde Complex Aqueous Solution This example illustrates the "slurry technique". To 10.4 g of a "high efficiency" type melamine-formaldehyde resin acid colloid (7.2% solids, prepared according to the method of Reference Example A) was added 96 g of distilled water at room temperature with gentle stirring. Add to the above, with stirring, a 4% aqueous solution viscosity of 30 mPa.s (30 cps) at 20 °C, about 1% acetate group, and 99.0% or more #10.
Commercially available polyvinyl alcohol powder of medium molecular weight fully hydrolyzed grade that passes through a sieve
Added 1.5g. This slurry is then heated with stirring to 85-95°C for 15 minutes, during which time
The polyvinyl alcohol appeared to dissolve completely. The clear solution of product was cooled to room temperature. PH
The solids content was about 2.8%, and the solution viscosity was low (less than 1 cps Brookfield). The polyvinyl alcohol/melamine-formaldehyde resin ratio was 2/1. An aqueous solution of this type of complex attempted at 12% total solids failed (gelled within minutes) and also failed at 4% solids (gelled within 16 hours).
However, it was stable at 2.9% solids. Example 2 This example is similar to Example 1 except that a melamine-formaldehyde resin acid colloid prepared according to the method of Reference Example B is used. In this case, the operation was virtually successful even in the presence of 5% total solids (although after 48 hours the viscosity had also increased to about 3.2 cps and traces of gel were also seen). The adsorption efficiency on bleached cellulose pulp at pH 4.0 was greater than 73% (about 18% on linear polyvinyl alcohol).
). Example 3 This example is similar to Example 1 except that a melamine-formaldehyde resin acid colloid prepared according to the method of Reference Example D is used. Successful products were produced at the 2% level and 2.7% solids, failed (gelled within 16 hours) at 6% solids, but remained stable at 2.9% solids. Example 4 4.05% of the polyvinyl alcohol used in Example 1 was added to a 250 ml Erlenmeyer flask containing a magnetic stirrer.
55.6 g of aqueous solution was added. To this solution, at room temperature, 10.5 g of a 7.15% solids melamine-formaldehyde resin acid colloid prepared according to the method of Reference Example D was added with stirring. Next, add 84g of distilled water,
The temperature was then increased to 65°C for 15 minutes. An active and stable aqueous complex solution was formed with a polyvinyl alcohol/melamine-formaldehyde weight ratio of 3/1 and 1.9% solids in the solution. Using other grades of polyvinyl alcohol, using various melamine-formaldehyde resin acid colloids, and using different polyvinyl alcohol/melamine-formaldehyde resin acid colloids.
Similar examples were successfully carried out using formaldehyde ratio polyvinyl alcohol copolymers and in the presence of corn starch or potato starch. Adding dilute (0.6%) melamine-formaldehyde resin acid colloid to a hot concentrated (10%) solution of polyvinyl alcohol was also successful. In fact, this is one of the preferred procedures for producing the aqueous polyvinyl alcohol/melamine-formaldehyde resin complex solutions of the present invention. Comparative Example 1 The polyvinyl alcohol used in Example 1
A 10.1% solution (66.6 g) was mixed with a 7.2% melamine-formaldehyde resin acid colloid (“high efficiency” type) (31.2
g) and 2.2 g of distilled water at room temperature to remove all solids.
A 3/1 polyvinyl alcohol/melamine-formaldehyde combination was obtained at 8.7%. This "solution"
The viscosity increases rapidly from 6.3 poiseuilles (measured using a Gerdner Holdt calibrated viscosity tube) after about 1 minute of mixing to over 148 poiseuilles after 30 minutes;
A hard gel was produced. Comparative Example 2 Add 158 g of water to 37.2 g of 7.2% melamine-formaldehyde resin acid colloid (“high efficiency” type),
Then, while stirring, 5.36 g of the polyvinyl alcohol powder used in Example 1 was added. The polyvinyl alcohol/melamine-formaldehyde ratio was 2/1 and the product solids in solution was 4%. The slurry was then heated to 85° C. with stirring. A gel formed within 16 hours. Comparative Example 3 Commercial polyvinyl alcohol of medium molecular weight fully hydrolyzed grade [14 mPas (cPs) at 20°C]
4% aqueous viscosity and about 1% acetate groups] in 100 mils of water.
607 TMM was added with stirring. TMM
It slowly dissolved. Next, add 2.9g of concentrated hydrochloric acid.
Lowered PH. After stirring at room temperature for 16 hours, a colloidal solution was formed. The activity of the product was very low (adsorption efficiency on cellulose pulp was only 8 at pH 4.5).
%). Example 5 Forming a novel product as suggested above,
Interaction (complexation) between polyvinyl alcohol and melamine-formaldehyde resin acid colloids
(1) Occurs when the components are mixed at somewhat higher concentrations than within the scope of the invention, but otherwise under the same or milder reaction conditions. Significant increase in viscosity: (2) Significant increase in absorption efficiency on cellulose pulp compared to the efficiency obtained when using linear polyvinyl alcohol, indicating polyvinyl alcohol with cationic groups. This is shown in table.

TABLE From the table it is clear that the level of adsorption of the polyvinyl alcohol/melamine-formaldehyde "high efficiency" complex on the pulp is still much higher than that of linear polyvinyl alcohol or even than that of commercially available cationic starch. (3) Spectral data also show interaction (complexation) between polyvinyl alcohol and melamine-formaldehyde fatty acid colloids. (a) Solution gave a colored reaction product with boric acid-iodine, as did linear polyvinyl alcohol. However, the strength of the complex was less than expected from linear polyvinyl alcohol. (b) In the infrared spectrum of the molded film air-dried at room temperature, the peak at 1000 cm ^-1 of the melamine-formaldehyde resin acid colloid disappears, suggesting that most of the methylol groups have reacted. In addition, approximately 830cm attributed to the −OH bond
The polyvinyl alcohol absorption of ^-1 is decreased, suggesting some kind of reaction by these groups. Example 6 Increased adsorption efficiency over linear polyvinyl alcohol and commercially available cationic wet-terminated additive (“Kymene”, a cationic polyamide containing amino groups, obtained from Hercules, possibly pre-reacted with epichlorohydrin) Bleached pulp mixtures (50/50
Other conditions were the same as in Example 5 using bleached northern softwood sulfite/bleached northern hardwood kraft. The results are summarized in table. Thus, 3/1
The polyvinyl alcohol/melamine-formaldehyde complex loses about 80% after 15 minutes of exposure to wet pulp.
while linear polyvinyl alcohol has an adsorption efficiency of only 18%. Additionally, polyvinyl alcohol/melamine-formaldehyde achieved its maximum adsorption level within 1 minute;
"Kymene" 557 did not achieve high levels of adsorption even after 5 to 10 minutes. Thus, polyvinyl alcohol/melamine-formaldehyde is
For Fourdrinier paper machines, it exhibits greater flexibility at the point of addition (fan pump, machine container, head box, etc.) than other cationic wet end additives.

[Table] Example 7 As described above, the polyvinyl alcohol of the present invention/
Solutions of melamine-formaldehyde complexes have excellent storage stability. Thus, no viscosity increase or gelation occurs for weeks to months, and the activity of the polyvinyl alcohol/melamine-formaldehyde complexes of the above examples remains high for at least two months. Also, unlike the situation in cationic starch solutions, there is no tendency for mold growth to occur. These complexes can also be manipulated by heat on a paper machine. That is, significant levels of permanent wet strength are obtained rapidly, significantly faster than with urea-formaldehyde resins, and perhaps as quickly as with linear melamine-formaldehyde resins. On the other hand, waste paper or broken recovery is faster than using melamine-formaldehyde resin by heating under very mild acid conditions (see Example 12). In this example, polyvinyl alcohol/
Quantitatively demonstrate the advantages of melamine-formaldehyde complexes in wet film strength. 100 feet of paper/
Made on a 36 inch wide Fourdrinier that operates in minutes. The pulp was a 70/30 hardwood bleached kraft/softwood bleached kraft mixture refined to 500 CSF. Additives were added to the feed at the Huang pump. For wet membrane testing, a wide strip was cut from the edge of the membrane on a couch roll and the tear force at two different water loads was measured on an Instron. Calculate the dehiscence length (strength) and interpolate the dehiscence length at the equivalent water load (35
% solids) and at additive concentrations at which they are commonly used in dry and/or wet paper strength applications. These are shown in Table 1.

It is found that most of these additives actually reduce the strength of the wet film (probably by interfering with the cellulose pulp-pulp interaction).
However, polyvinyl alcohol/melamine-formaldehyde complexes do increase wet film strength. Example 8 This example illustrates the higher retention of cellulose fibers possible by using polyvinyl alcohol/melamine-formaldehyde as an additive. Processing advantages resulting from high retention forces during first pass have been recognized in the literature (KWBritt, Paper Trade Journal, April 15,
(1977, p. 36). Also, the retention of cellulose fibers (and also pigments and/or fillers) is significantly greater at the high shear rates experienced in commercial paper mills than at the lower shear rates in routine laboratory tests. It is well known that it can be low. K. Britt examines cellulose fibers, fillers and pigments in the laboratory under conditions that approximate the agitation experienced by the pulp stock as it flows out within the first impression of the wire of a paper machine. We developed a single-screen type device for measurement. This is called a "dynamic outflow jar" or "Britt Jar." this is
TAPPI Report No. 57 “Retention of Fine Solids
During Paper Manufacturing” (9/1/75)
Described in the Appendix to Chapter 8 by KWBritt. Following the Britt procedure, the following results, summarized in Table 1, show that for the 3/1 PVA/MF(HE) complex, various additives were compared with two commercially available cationic starches. obtained at various concentrations and PH of pulp raw material.

[Table] N ^(c)
5.5 50.8
6.5 54.3

Table: It is clear that PH 4.5 is optimal for polyvinyl alcohol/melamine-formaldehyde retention purposes, while PH 6.5 is probably optimal for cationic starch. It is also clear that for each additive, at its optimum PH, polyvinyl alcohol/melamine-formaldehyde outperforms cationic starch at all additive concentrations. On the unbleached kraft pulp used above, and also on the bleached pulp, clay or pigment (TiO ₂ )
Similar benefits were seen in the retention of . Table Additives (Concentration 2%) Clay Retention% (a) None ~2 Cationic Starch 15 MF (HE) Resin 12 3/1PVA/MF 28 (a) 50/50 Bleached Softwood Sulfite/Bleached Hardwood Kraft Pulp, CSF ~ 500. Use blitzjer at 1000 rpm. Cationic starch is "Cato"
9. Polyvinyl alcohol/melamine-formaldehyde was prepared by the method of Example 4.

[Table] To demonstrate that these high levels of fiber retention were not due to excessive flocculation, which could damage the paper quality or processing properties, the optical properties of the resulting paper I researched it and found it to be excellent. This is discussed below in Example 9. The following examples demonstrate reinforced paper and paper-related products that can be obtained through the use of polyvinyl alcohol/melamine-formaldehyde complexes as additives in paper machines. Example 9 A procedure for determining reflectance using paper produced on a Fourdrinier machine as described in Example 7.
Measure the scattering coefficient by TAPPI method T218-05-69, then use the SW value TAPPI425-05-75 data, divide by the reference weight, multiply by 10000, and calculate cm ² /
Values in g were obtained. The data are shown in the table for paper containing 10% clay.

【table】

TABLE The above shows increased scattering when using the PVA/MF complex, which suggests better paper production and/or filler distribution within the paper. Example 10 Noble and Wood
A handsheet is produced in a sheet mold (8″ x 8″), rolled between rolls,
It is then dried in a Noble & Wood Model E-8 dryer. The pulp was unbleached Western Kraft refined to CSF600. tensile strength
Measured by TAPPI494-05-70. The results are shown in Table 1.

[Table] From these data, it can be seen that the PVA/MF complex exhibits superior dry strength and strength to the commercially available additives, and in fact, PVA/MF does not exceed the 2% reference standard. It is even better at a concentration of 0.7% than at a concentration of 0.7%. Such benefits are also maintained when fillers are present. Example 11 PVA/MF complexes are also very effective paper wet strength agents. This is shown in table.

Table: The PVA/MF complex shows better wetting properties than commercially available linear MF resins or, of course, cationic starch, which is known to have no wet strength properties. Indicates strength, wet tensile energy absorption (TEA). Epoxidized versions of aminopolyamides appear to be somewhat better than the PVA/MF complexes of the present invention in terms of wet strength (wet cleavage length). However, epoxidized aminopolyamides are much more expensive and are far inferior to polyvinyl alcohol/melamine-formaldehyde products in terms of ease of scrap or waste paper recovery. Example 12 This example illustrates that epoxidized aminopolyamide ("Kymene" 557) is far inferior to the polyvinyl alcohol/melamine-formaldehyde complex of the present invention in terms of ease of scrap or waste paper recovery. do. This is shown in the table,
There, we make Fourdrinier from bleached kraft pulp.
The data for the paper made above shows that heating the paper in a very dilute acid solution causes the paper to lose its wet strength. Such loss of strength is, of course, necessary for easy paper recovery. Apparently, papers containing polyvinyl alcohol/melamine-formaldehyde additives crumble more easily in dilute acids than linear melamine-formaldehyde resins, and quite obviously, much more easily than epoxidized aminopolyamides. collapses easily.

[Table] Example 13 Raw potato starch/MF at a weight ratio of 3/1
(HE) 2% aqueous solution 3/1PVA/MF
It was produced in the same manner as the (HE) complex aqueous solution. In addition, a 3/1/1 starch/PVA/MF (HE) complex aqueous solution was produced in a similar manner. In these cases, MF(HE) resin acid colloids were prepared as in Reference Example A, and the latter were then reacted as in Example 4 with potato starch and/or polyvinyl alcohol. Starch/melamine-formaldehyde and starch/polyvinyl alcohol/melamine-
Formaldehyde solutions were only stable for less than 3 weeks, whereas polyvinyl alcohol/melamine-formaldehyde was stable for more than 3 months. Handsheets were made using bleached sulfite pulp. The properties of the handsheet are shown in Table XI along with a reference standard that does not contain any wet end additives. Thus, the superiority of 3/1 polyvinyl alcohol/melamine-formaldehyde over 3/1 starch/melamine-formaldehyde is demonstrated both in solution stability and in paper quality. In fact, in some characteristics,
3/1 polyvinyl alcohol/melamine-formaldehyde at 0.7% is equal to or superior to 3/1 starch/melamine-formaldehyde at a concentration of 2%. Also, 3/1/1 starch/polyvinyl alcohol/melamine-formaldehyde is superior to 3/1 starch/melamine-formaldehyde.

[Table] Using clay at 10% concentration in paper, similar advantages of 3/1 PVA/MF over 3/1 starch/MF can be seen in tearing, folding resistance and dry and wet tearing length and tensile strength. Seen in energy absorption. Again, 3/1/1 starch/PVA/MF had several advantages over 3/1 starch/MF. The results are summarized in Table XII.

EXAMPLE 14 This example illustrates the use of polymeric aldehydes to modify PVA/MF complexes.
In operation (C), a "high efficiency" melamine-formaldehyde resin acid colloid was prepared as in Reference Example A. In operations (D) and (E), instead of adding formaldehyde, the MF resin acid colloid is "aged".
Acetaldehyde was added at this time. These were then added to the pulp and handsheets were made. The table shows the adsorption of additives to the pulp and the handsheet properties of the resulting paper. It is clear that the results when adding acetaldehyde were as good as when adding formaldehyde, at least in terms of drying properties.

[Table] Example 15 In this example, dialdehyde and glutaraldehyde were added during the MF resin acid colloid aging process.
The utility of PVA/MF complexes is illustrated. Operation (B), (C)
and (D) were carried out following the general procedure of Example 14. The data are summarized in the table comparing the addition of glutaraldehyde to formaldehyde. The solution stability of the glutaraldehyde modified product was much lower than that of the formaldehyde modified product. Nevertheless, when used only a short time after production, filler retention in the pulp is surprisingly high using glutaraldehyde. Furthermore, although the concentration of the product added to the pulp was lower than in Example 14, good paper quality was obtained. Improved solution stability (at least 5 days) was obtained by adding lower levels of glutaraldehyde (13% by weight based on MF resin).

【table】

Claims (1)

[Scope of Claims] 1. A complex of a polyvinyl alcohol polymer and a cationic melamine-formaldehyde resin acid colloid in a polyvinyl alcohol/melamine-formaldehyde resin acid colloid weight ratio of 1/1 to 5/1 on a dry weight basis, and 0.7 wt. % to 6% by weight of water. 2. The aqueous composition according to claim 1, having a solids content of 0.7 to 3.75% by weight. 3 The polyvinyl alcohol polymer is at least
The aqueous composition according to claim 2, which is 99 mol% hydrolyzed. 4 Polyvinyl alcohol polymer in water at 30℃
4. The aqueous composition according to claim 3, having an intrinsic viscosity of 0.3 to 1.4 g/dl, measured at a concentration of 0.5 g/dl. 5 Polyvinyl alcohol polymer is 0.5 to 1.1
The aqueous composition according to claim 4, having an intrinsic viscosity of dl/g. 6 Melamine-formaldehyde resin acid colloid is added to trimethylolmelamine dissolved in water with 8 to 100% by weight, based on the weight of trimethylolmelamine, of an aldehyde having up to 10 carbon atoms, and trimethylolmelamine 1
3. The aqueous composition of claim 2, which is prepared by aging said solution in the presence of 0.6 to 0.2 mol per mol of hydrochloric acid. 7. said aldehyde is selected from the group consisting of formaldehyde and its homologues, substituted aldehydes and polyaldehydes;
The aqueous composition according to claim 6. 8 The aldehyde can be converted into formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, 2-ethylhexylaldehyde, phenylacetaldehyde, chloroacetaldehyde,
8. The aqueous composition of claim 7, comprising a composition selected from the group consisting of 3-methoxypropionaldehyde, aldol, crotonaldehyde, glutaraldehyde, glyoxal, adipaldehyde and terephthaldehyde. 9. The aqueous composition according to claim 7, wherein the aldehyde is formaldehyde. 10 The aldehyde is acetaldehyde,
The aqueous composition according to claim 7. 11. The aqueous composition according to claim 7, wherein the aldehyde is glutaraldehyde. 12. An aqueous composition according to claim 2 having a solids content of 2 to 3% by weight. 13. The aqueous composition according to claim 3, wherein the weight ratio of polyvinyl alcohol/melamine-formaldehyde resin acid colloid is from 2/1 to 3/1 on a dry basis. 14 A complex of a polyvinyl alcohol polymer and a cationic melamine-formaldehyde resin acid colloid in a polyvinyl alcohol/melamine-formaldehyde resin acid colloid weight ratio of 1/1 to 5/1 on a dry weight basis, and 0.7% to 6% by weight
1. A method of producing an aqueous composition comprising: (a) producing a cationic melamine-formaldehyde resin acid colloid; (b) sufficient water to provide a solids content of % by weight; The colloid is mixed with polyvinyl alcohol and the polyvinyl alcohol/melamine-formaldehyde resin acid at a given mixing temperature in proportions such that the weight ratio of the polyvinyl alcohol/melamine-formaldehyde resin acid colloid is from 1/1 to 5/1 on a dry weight basis. A method characterized by mixing in the presence of sufficient water to provide a solids content of 0.7% to 6% by weight for a sufficient time to form a resin complex. 15. Process according to claim 14, characterized in that the solids content is between 0.7 and 3.75% by weight. 16 The melamine-formaldehyde resin acid colloid and polyvinyl alcohol were heated at around room temperature 24
Claim 1 consisting of time mixing.
The method described in Section 5. 17. The method of claim 15, comprising mixing the melamine-formaldehyde resin acid colloid and polyvinyl alcohol at a temperature of 30 to 90°C for 3 to 15 minutes. 18. slurrying the polyvinyl alcohol powder or granules in the melamine-formaldehyde resin acid colloid, and heating and stirring the slurry at a temperature of 80 to 95°C for 0.25 to 2 hours or until the polyvinyl alcohol dissolves;
The method according to claim 15. 19. The method of claim 15, comprising using enough water to give a solids content of 2 to 3% by weight. 20. The method of claim 19, wherein the polyvinyl alcohol/melamine-formaldehyde resin acid colloid weight ratio is from 2/1 to 3/1 on a dry basis. 21 Dissolve polyvinyl alcohol in water by mixing and heating to make a 10% by weight solution, add the hot polyvinyl alcohol solution to 0.6% by weight melamine-formaldehyde resin acid colloid, and add the melamine-formaldehyde resin acid colloid to a temperature near room temperature. and gently stir the resulting mixture to 15
Claim 1 consisting of stirring for a minute.
The method described in Section 9. 22 The polyvinyl alcohol polymer is at least 99 mol% hydrolyzed and in water at 30°C.
21. A method according to claim 15, 19 or 20, characterized in that it has an intrinsic viscosity of 0.5 to 1.1 dl/g, measured at a concentration of 0.5 g/dl.