MXPA00001718A

MXPA00001718A - Cellulose filter paper saturant

Info

Publication number: MXPA00001718A
Application number: MXPA/A/2000/001718A
Authority: MX
Inventors: Norman Lifshutz
Original assignee: Hollingsworth And Vose Company
Priority date: 1997-09-18
Filing date: 2000-02-18
Publication date: 2001-11-21

Abstract

An aqueous saturant for cellulose papers comprising a hydrolyzedpolyvinyl alcohol and a formaldehyde resin, wherein the polyvinyl alcohol and the formaldehyde resin are substantially or completely dissolved in the system. The invention is also directed to methods for making and using the saturant. The system is also directed to paper, e.g., filter paper, made with the saturant as well as methods for making paper with the saturant.

Description

PAPER SATURANT CELLULOSE FILTER FIELD OF THE INVENTION i m7Dnp r- »t? Ipel's oils specifically to the saturants d paper filter d? cellulose.

BACKGROUND OF THE INVENTION Cellulose filter papers are well known for many applications, such as automotive and heavy-duty oil and air filtration. In general, these are produced by dispersing cellulose fibers, such as wood pulp, in water and filtering the fiber suspension through screens or continuous meshes of a paper machine. Typically, the resulting paper is dried once, then saturated with an aqueous or non-aqueous solution or polymer or resin suspension, and finally dried again. Otherwise, while still wet, the newly formed paper is saturated with an aqueous or non-aqueous solution or suspension of polymer or resin, and then dried only once. The dried, saturated paper can then be folded, corrugated or formed into a filter configuration, and possibly subjected to a thermal process to develop its final properties. To work properly in oil and air filtration applications in automotive and heavy-duty (trucks), the saturant must confer high Mullen combustion resistance, tensile strength and specific stiffness under curing, humidity or elevated temperature conditions. In addition, since wood pulp is usually much less expensive than the polymers and resins comprising the saturant, it is economically desirable to obtain these mechanical properties by using the lowest possible saturant content in the finished paper.

A traditional method to characterize stiffness in a range of elevated temperatures is through the use of a Dynamic Mechanical Analyzer in bending beam mode, for example, DMA-7 by Perkin Elmer. Such an instrument can measure the "in-phase" flexural modulus (elastic stiffness), and the "out-of-phase" loss modulus of the paper as the temperature is scanned from about room temperature to about 200 ° C. Typically, the above known saturants have been formaldehyde resins of low molecular weight phenol, urea or melamine, dissolved in organic solvent or water. Other saturants have included aqueous dispersions of high molecular weight polymers such as polyvinyl acetate, polyvinyl chloride or dispersed polyacrylic esters ns. but not dissolved, in or combinations of these polymers U.S. Patent No. 4,461,858 (Adelman), for example, discloses a colloidal acidic system nsn crab in cellulose pulp slurries that include a product of the polyvinyl alcohol interaction. melamine formaldehyde-aqueous, stable resin containing a polyvinyl alcohol polymer and a cationic colloid of melamine-formaldehyde resin in an acid colloid of polyvinyl alcohol / melamine-formaldehyde resin. U.S. Patent No. 4,324,833 (Yau) discloses a mat binder for an aqueous, phenolic resin-urea wet process consisting of an aqueous solution of partially methylated melamine-formaldehyde resin and a polyvinyl alcohol, the aqueous solution having a pH within the range from about 3.5 to about 6.5.

SUMMARY OF THE INVENTION The invention is directed to a filter paper prepared with a saturant consisting of a hydrolyzed polyvinyl alcohol and a formaldehyde resin, wherein the polyvinyl alcohol and the formaldehyde resin are substantially or completely dissolved in the system. The saturant is applied to a base filter paper, such as a cellulose base paper, so that the saturant forms approximately 5% to 20% of the filter paper in the dry state.

Of the Saturant used with the invention soluncrion asnmilons? S Ul? high molecular polyvinyl alcohol, complete with iodide and a resin containing methylol, of low molecular weight, soluble in water. The methylol-containing resin is preferably a formaldehyde resin of phenol, urea or melamine. The formaldehyde resin acts as an interlacing agent for polyvinyl alcohol. In one embodiment, the system includes a solution of polyvinyl alcohol and a phenol in formldehyde resin having a pH in the range of about .5 to about 10.5. It is possible to use an inorganic salt as a catalyst to aid in the crosslinking of the urea and melamine reams. The invention is also directed to methods for 1 elaborate and use the water based saturant.

BRIEF DESCRIPTION OF THE DRAWINGS A more complete understanding of the present invention and the advantages and characteristics thereof will be They are more easily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings, wherein: FIGURE 1 is a graph comparing the stiffness of the cellulose paper prepared in accordance with the present invention, containing polyvinyl alcohol phenolic resin and cellulose paper prepared with any resin alone; FIGURE 2 is a graph comparing the rigidity of the cellulose paper prepared according to different embodiments of the present invention; cellulose paper prepared according to the different embodiments of the present invention; and The FIGURE. 4 is a graph comparing the rigidity of the cellulose paper prepared according to the different embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION The invention is directed to a filter paper formed with a saturant consisting of an aqueous solution of hydrolyzed polyvinyl alcohol and a formaldehyde resin, wherein the formaldehyde resin and the polyvinyl alcohol are completely or substantially dissolved. The polyvinyl alcohol is present in an amount sufficient to allow the system to function as a saturant in the cellulose paper manufacturing operations. Preferably, the polyvinyl alcohol is present in the dry saturant composition in an amount in the range of from about 25% to 95% by weight. One skilled in the art will appreciate that other ranges are within the scope of the invention. The polyvinyl alcohol is sufficiently hydrolyzed so that, when combined with the formaldehyde ream and water, the formaldehyde resin is crosslinked with the polyvinyl alcohol. Preferably, the polyvinyl alcohol is hydrolysed at least about 98%. However, one skilled in the art will appreciate that other ranges are within the scope of the invention. Suitable polyvinyl alcohols include Airvol® 103, 107, 125 and 165, available from Air Products Inc .; and Elvanol® 70-06, 71-30 and 90-50, available from duPont de Nemours & Co. The molecular weight of polyvinyl alcohol is, in general, in the range of 10,000 to 190,000. In one embodiment, the molecular weight of the polyvinyl alcohol is in the range from about 30,000 to about 50,000. One skilled in the art will appreciate that other polyvinyl alcohols having other ranges of molecular weights may also be used. The formaldehyde resin of the phenol, urea or melamine containing methylol is preferably soluble in water and has the functionality to act as a crosslinker or curing agent for the polyvinyl alcohol resin. Preferably, the crosslinking ream has an average degree of polymerization of 1 to 3. The phenol formaldehyde resins include Arofene 72155, Arotap 8095 and Arofe DR 343, all available from Ashland Chemical Co. An exemplary melamine formaldehyde resin includes Parez 707, available from Cytec Industries. The formaldehyde resin is usually present in a dry saturant composition in an amount from about 75% to 5% by weight, but other ranges are within the scope of the invention. Preferably, the formaldehyde resin is a phenol resin. It is also possible to use suitable urea and melamine resins. Exemplary ureas and melamines include the urea glyoxal formaldehyde condensate (BERSET 2300, available from Bercen, Inc. of Cranston, Rhode Island), and melamine formaldehyde resins such as BERSET 2003 (available from Bercen, Inc. of Cranston, Rhode Island), SEQUA MEL-80 (available from Sequa Chemicals, Inc. of Chester, South Carolina), AURAMEL 484, AURAMEL M-75 and AURAREZ 963 (available from Sybron-Tanatex, Inc). Optionally, it is possible to use an acid salt as a catalyst to aid in the crosslinking of the urea and formaldehyde resins. Suitable acid salts are those formed from a weak base and a strong acid which, with hydrolysis, produce a strong acid. Exemplary acid salts useful as catalysts in this invention include magnesium chloride, ammonium sulfate, ammonium nitrate, ammonium chloride and aluminum chloride.

A particularly preferred acid salt is magnesium chloride. Such an acid salt is generally used in a concentration in the range of about 2.5 to 7.5% by weight solids in the saturant. The saturant generally has a pH high enough to maintain all or practically all of the soluble formaldehyde resin. The pH of the saturant can be adjusted with a base to be within the range of 7.5 to 10.5. Suitable bases include a fixed base such as potassium or sodium hydroxide, or a fugitive base such as ammonium hydroxide. Other pH ranges are within the scope of the invention. The water-based saturant of the invention can be prepared with conventional preparation techniques. 15 Polyvinyl alcohol usually dissolves in water at 85 ° F and is cooled with additional water. The pH is adjusted and then the crosslinking resin is added. During use, the saturant imparts improved stiffness and strength to the cellulose filter paper under a variety of papermaking conditions. For example, the saturant imparts improved stiffness and strength during normal conditions and / or wet conditions when applied to cellulose filter papers at lower than normal levels. The saturant can be applied at a concentration of 5% to 25% by weight in water to achieve a The content of the binder is from 5% to 20% by weight in the dry finished paper, in a preferred saturant which is suitable for manufacturing filter paper. cellulose, the polyvinyl alcohol is present in an amount in the range from about 50% to 75% on a dry basis, and the formaldehyde resin of phenol is present in an amount from about 50% to 25% on a dry basis. it is 65% polyvinyl alcohol and 35% phenol formaldehyde resin, on dry basis The content of the preferred medium is about 10% by weight of the polymer in the dry finished paper.This saturant can be applied to the paper in different forms, including a primer, cylinder for rotogravure or other techniques known to the skilled artisan.The preferred method of application is by primer.The invention is furthermore described in the following illustrative examples.A one skilled in the art will further appreciate that It is possible to make minor modifications to the invention described herein without departing from its proposed scope. All references indicated herein are incorporated as a reference in their entirety. ÍMÉA & ¿jSsSg in EXAMPLE 1 In this example, the saturants of the invention were first prepared by dissolving polyvinyl alcohol in water at 185 ° F, cooling with additional water, adjusting the pH and then adding the formaldehyde resin. The solutions of the resins and the polymers of Table 1 were prepared at different DbtencionC-uon.es in water and used to saturate a base paper of cellulose Dbtenció in a laboratory primer. The resulting saturated leaves were dried in photoseaters, and the resulting resin content in the finished sheets was determined by the Dbtention of weight of the leaf. Table 1 mentions the measured content of the resin in each of the samples.

T? RT.S 1 The resulting sheets were tested on a dynamic Perkin Elmer DMA-7 mechanical analyzer in beam mode Bending using 20 mm x 5 mm samples cut in the direction of the paper machine. The real extension of the beam was 15 mm. The samples were run twice in a temperature range from about 25 to 240 ° C. The sheets were run the first time to characterize the rate of curing of the material, and the second time to characterize the mechanical properties of the complete curing of the sheet saturated with resin. The results are shown in Figure 1.

EXAMPLE 2 Solutions were prepared as specified in Table 2 and used to saturate an all cellulose base paper, standard in a laboratory scanner. The resulting saturated leaves were dried in photoseaters, and the resulting resin content in the finished leaves was determined by the weight gain of the sheet. Table 2 mentions the resin measured for each of the samples. The resulting sheets in the DMA-7 were tested again according to Example 1, and the results are shown in Figure 2. Figure 2 shows that the solution D5, having the highest PVOH / PhOH ratio of the solutions (72 : 25) works better. Then the leaves were cured. After curing the leaves for 10 minutes at 300 ° F, the tensile strength MD the Mullen combustion resistance and the MD stiffness in the resulting lows before r after 5 minutes of soaking in a 2.5% solution were measured. of a cleaner 1 í QII "i í - • r ~ o ~ r1 vtr -ia 1 T cr?" R "r >? T > oHaHoc; Ci Fí ras on aor'n V Vii'nnßHn mentioned in Table 2.

EXAMPLE 3 solu®uu &J | £ were prepared as specified in Table 3 and were used to saturate a whole cellulose base paper, standard in a laboratory primer. The resulting saturated leaves were dried in photoseaters, and the resulting resin content in the finished leaves was determined by obtaining the weight of the sheet. Ia Table 3 mentions the results of the measured resin of each of the samples. The resulting sheets in the DMA-7 were tested again according to Example 2, and the results are shown in Figure 3. The leaves were then cured for 10 minutes at 300 ° F. The MD tensile strength, the Mullen combustion resistance and the MD stiffness of the resulting sheets were measured again before and after 5 minutes of soaking in a 2.5% solution of a commercial liquid cleaner. The physical properties in wet and dry are also mentioned in Table 3.

TABLE 3 EXAMPLE 4 Solutions were prepared as specified in Table 4 and used to sasture a standard cellulose base paper in a laboratory primer. The resulting saturated sheets were dried in photo dryers, and the resulting resin content in the finished sheets was determined by obtaining the weight of the sheet. Table 4 mentions the result of the measured resin of each of the samples. The resulting sheets in the DMA-7 were tested again according to Example 1, and the results are shown in Figure 4. Again, after curing the sheets 10 minutes at 300 ° C, the tensile strength was measured. MD, the Mullen combustion resistance and the MD stiffness of the resulting sheets before and after 5 minutes of soaking in a 2.5% solution of a commercial liquid cleaner. The physical properties in dry and wet are also mentioned in Table 4.

Ta a 4 EXAMPLE 5 were prepared solutions as specified in Table 5 with different urea resins and melamine formaldehyde solutions ^ re ^ plowings were then used r ~? Ara saturate a to ^ the basis all standard cellulose in a ^ subtractor laboratory . All solutions included Berchem 3009 magnesium chloride that functions as a catalyst for a crosslinking reaction that includes reams of formaldehyde urea and melamine. The resulting saturated leaves were dried in photo dryers, and the resulting resin content in a finished "dry" sheet was determined by the weight gain of the leaf, The leaves were cured for 10 minutes at 30 ° F, and tested for MD tensile strength, MD stiffness and Mullen combustion resistance. The leaves were also rinsed for 1 minute in a 2.5% solution of a commercial liquid cleaner; the resulting "wet" sheets were then tested again for MD tensile strength, MD stiffness and Mullen combustion resistance. These physical properties of the "dry" and "wet" leaves are also included in Table 5.

TABLE 5

Claims

to CLAIMS

1. A filter paper containing: a cellulose base paper substrate; and a saturant formed from an aqueous solution of about 25% to 95% by weight of polyvinyl alcohol and about 5% to 75% by weight of a formaldehyde resin, the saturant forming about 5% to 20% of the filter paper in a dry state .

2. The filter paper of claim 1, wherein the polyvinyl alcohol is substantially all hydrolyzed.

3. The filter paper of claim 1, wherein the molecular weight of the polyvinyl alcohol is between about 10,000 and about 190,000.

4. The filter paper of claim 1, wherein the formaldehyde resin has an average degree of polymerization of 1 to 3 and is effective to crosslink the polyvinyl alcohol.

5. The filter paper of the 1, where the formaldehyde resin is a resin that contains methylol.

6. The filter paper of claim 1, wherein the formaldehyde resin is selected from the group consisting of phenol, urea and melamine.

7. A method for manufacturing a filter paper, comprising: providing a cellulose base paper substrate;

forming an aqueous saturant having substantially dissolved therein about 25% to 95% by weight of polyvinyl alcohol and about 5% to 75% by weight of a formaldehyde resin; and applying the saturant to the base paper in an amount sufficient to obtain, on drying, a filter paper having the saturant at about 5% to 20% by weight. The method of claim 7, wherein the polyvinyl alcohol is substantially all hydrolyzed.

9. The method of claim 1, wherein the molecular weight of the polyvinyl alcohol is between about 25,000 and about 190,000.

The method of claim 7, wherein the formaldehyde resin has an average degree of polymerization of 1 to 3 and is effective to crosslink the polyvinyl alcohol.

The method of claim 7, wherein the formaldehyde resin is a resin containing methylol.

The method of claim 7, wherein the formaldehyde resin is selected from the group consisting of phenol, urea and melamine.

The method of claim 7, wherein the formaldehyde resin is selected from the group consisting of urea formaldehyde resins and melamine formaldehyde resins.

14. The method of claim 13 further includes providing with the aqueous saturant a salt catalyst.

Inorganic srt pnpcen ratio in the firl 1 or fifi approximately 2.5 7.5% by weight of solids in the saturant. The method of claim 14, wherein the inorganic salt catalyst is selected from the group consisting of magnesium chloride, magnesium sulfate, ammonium chloride, aluminum chloride and ammonium nitrate.

16. A filter paper, which contains: a cellulose base paper substrate; and a saturant formed from an aqueous solution of about 25% to 95% by weight of polyvinyl alcohol and about 5% to 75% by weight of a crosslinking agent, the saturant forming about 5% to 20% of the filter paper in a dry state . 1 .

The filter paper of claim 16, wherein the crosslinking agent is a formaldehyde resin.

18. The filter paper of claim 17, wherein the formaldehyde resin is a resin containing methylol.

19. A method for making filter paper consists of: providing a cellulose base paper substrate; forming an aqueous saturant having substantially dissolved therein about 25% to 95% by weight of polyvinyl alcohol and about 5% to 75% by weight of a crosslinking agent; and apply the saturant to all the base paper in a ~ r >

enough quantity for bt p ^. & r. the filter paper having the saturant at about 5% to 20% by weight.

20. The method of the claim? , wherein the crosslinking agent is a formaldehyde resin.

21. The method of claim 19, wherein the formaldehyde resin is a ream containing methylol.

* ™ ¡'SUMMARY OF THE INVENTION

An aqueous saturant for cellulose papers containing a hydrolyzed polyvinyl alcohol and a formaldehyde resin is described, wherein the polyvinyl alcohol and the formaldehyde resin are practically or completely dissolved in the system. The invention also addresses the methods for manufacturing and using the saturant. The system is also aimed at paper, for example, filter paper, prepared with the saturant as well as the methods for making paper with the saturant.