Abstract:
A paper-making furnish, comprising poly(paravinyl phenol), also known as poly(hydroxy styrene), in admixture with polyethylene oxide, and a process for retaining fine particles in paper-making comprising adding poly(paravinyl phenol) and polyethylene oxide to a paper-making furnish, are disclosed.

Description:
This application is a continuation-in-part of application Ser. No. 8/036,745 filed Mar. 25, 1993, now abandoned. 
    
    
     This invention relates to fine-particle retention aids for paper-making processes, comprising phenolic compounds. 
     BACKGROUND OF THE INVENTION 
     Phenolic resins with sulfur or formaldehyde are described in U.S. Pat. No. 4,070,236 as being useful as additives for improving fine particle retention in paper manufacturing when used in conjunction with a poly(alkylene oxide) having a molecular weight of 4 to 7 million, specifically the preferred poly(ethylene oxide) (PEO) or co-condensed polyethylene/polypropylene oxide; poly(propylene oxide) is mentioned (but there would appear to be a problem of solubility with polyalkylene oxides other than poly(ethylene oxide)). 
     K. R. Stack, L. A. Dunn, and N. K. Roberts, show in &#34;Study of the Interaction Between Poly(ethylene oxide) and Phenol-Formaldehyde Resin&#34;, Colloids and Surfaces (61), 1991, pp 205-218, how varying the environment and certain properties of the phenol-formaldehyde resin can affect the performance of the phenol-formaldehyde resin/PEO system. T. Lindstrom and G. Glad-Nordmark in &#34;Network Flocculation and Fractionation of Latex Particles by Means of a Polyethyleneoxide-Phenolformaldehyde Resin Complex&#34;, J. Colloid and Interface. Science, Vol. 97, No. 1, January 1984, pp 62-67 propose a mechanism they refer to as a &#34;. . . transient network . . . &#34; of hydrogen bonded poly(ethylene oxide) and phenol-formaldehyde resin which swept the fine particles from the system. 
     The references indicate that the effectiveness of poly(ethylene oxide) for improving fine particle retention increases with its molecular weight; the effectiveness below a MW of 2 million being poor and a MW of 4 to 7 million being desirable. 
     However, the combination of phenol-formaldehyde resin and poly(ethylene oxide) functions less effectively as the pH is reduced below 5. The resin component also introduces formaldehyde or naphthol into the paper-making system. 
     There is therefore a need for a new retention aid that avoids the introduction of hazardous substances such as formaldehyde, and that can function at a lower pH, such as under 5, as well as at higher pH levels conventionally used in paper-making. 
     SUMMARY OF THE INVENTION 
     According to the invention, a paper-making furnish containing a 15 phenolic compound in admixture with a soluble polyalkylene oxide having a molecular weight over one million as a retention aid for retaining fine particles, characterized in that the phenolic compound is poly(paravinyl phenol), also known as poly(parahydroxy styrene), and preferably is poly(ethylene oxide). 
     Also according to the invention, a process for retaining fine particles in paper-making comprising adding to a paper pulp slurry a phenolic compound in admixture with a soluble polyalkylene oxide preferably poly(ethylene oxide) having a molecular weight over one million and a poly(paravinyl phenol). 
     It is preferred to add alum and/or a cationic polymeric coagulant, such as a polyamine, to the composition according to the invention, to improve retention by coagulating fine particles to a larger size that is better retained by this invention. 
     The amount of the retention aid used is preferably such that the poly(ethylene oxide) added to the pulp is in the range of about 0.01% to about 0. 1% by weight of the paper furnish, more preferably from 0.01% to about 0.05%, and the poly(paravinyl phenol) is preferably in the ratio of 0.5 to 10 times the weight of the poly(ethylene oxide). 
     The poly(paravinyl phenol) functions at pH levels under 5, as well as at higher pH levels, and avoids the introduction of formaldehyde or other hazardous substances into the paper-making system. 
     The molecular weight of the poly(ethylene oxide) should be as high as possible, preferably between 4 and 7 million and most preferably at least 5 million. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The paper can be made with bleached or unbleached chemical pulps, mechanical pulps, chemi-mechanical pulps, or recycled pulps. It can include conventional additives such as sizing agents, fillers such as titanium dioxide, calcium carbonate, kaolin clay, or talc, and polymeric additives such as wet strength resins, polyamines or polyamide-amines, or polyacrylamide polymers or copolymers of acrylamide. 
     The retention system functions well at a wide range of ratios of the poly(ethylene oxide) to the poly(paravinyl phenol). Conventional tests, such as those described below in the Examples, can be done on a particular paper stock sample to determine the optimum ratio for a given application of the composition and process according to the invention. 
     Within the preferred ratio of 0.5 to 10 times the weight of the poly(ethylene oxide), a more preferred ratio of poly(paravinyl phenol) to poly(ethylene oxide)is 6:1 to 1:1.25 (0.8 to 6 times). The most preferred embodiment of the invention uses a ratio of poly(paravinyl phenol) to poly(ethylene oxide) of about 2:1 to about 3:1, with cost considerations favoring the lowest effective ratio in a particular paper-making system. 
     A phenolic resin currently in use as an additive in conjunction with polyethylene oxide, Reichhold resin BB-139 from Reichhold Chemicals, was compared to poly(paravinyl phenol) as a retention aid in paper furnishes collected from commercial mills, and these control results are compared with those obtained by using the composition and process according to the invention: 
    
    
     EXAMPLES AND CONTROL EXPERIMENTS 
     Procedure: 
     The retentions and drainage were measured in a drainage jar referred to as the Portable Dynamic Drainage Tester, similar to drainage jars used in the industry with the exception that additives are added to an aliquot that is agitated before it is added to the drainage jar. Since the Portable Dynamic Drainage Tester has an open outlet, drainage starts immediately upon addition of the sample to the tester. 
     The procedure for the Portable Dynamic Drainage Tester (PDDT) is to measure about 200 ml of a stock sample at headbox consistency into a 1000 ml plastic graduated cylinder. This sample is inverted six times, then any additive is added to the cylinder, and an additional six inversions of the cylinder are made before pouring the sample into the top of the PDDT. If more than one additive is used, the sample is inverted six times between additives, with an additional six inversions between the last additive and pouring the sample into the PDDT. For these experiments the PEO, phenolic resin, and poly(paravinyl phenol) were diluted to 0. 1% for additions. The poly(paravinyl phenol) was dissolved in distilled water by adding dilute sodium hydroxide dropwise until the poly(paravinyl phenol) dissolved. 
     Chemical additive addition is noted below in pounds per ton, where pounds are the pounds of chemical and tons are the tons of paper furnish in the 200 ml. sample. For example, I ml. of 0.1% PEO in 200 gms. of 0.5% wood pulp is equivalent to 0.1% or two pounds of PEO per ton of furnish. In these examples, the phenol-formaldehyde resin or poly(paravinyl phenol) was always added before the PEO. 
     The PDDT agitator is operating at 750 rpm with the bottom valve open at the time of sample addition. The time is noted for 50, 75, and 100 ml of liquid to drain from the sample during the test. When 100 ml. of &#34;white water&#34; is collected the bottom valve is closed and the solids in the white water is determined. This white water solids value is compared to total solids for first pass retention and to fines content for fine particle retention. Fine particle retention is a more sensitive test. 
     The fines content is defined as the dry weight of material per 100 ml of white water that passes through the screen of the PDDT when the stirrer at 750 rpm is held against the screen during an experimental run with no polymers added. 
     In Tables 1 and 2, the comparative tests and Examples used poly(paravinyl phenpoll) with a MW ranging from 1,500 to 7,000 from Polysciences Inc., Warrington, Pa. Catalogue No. 6257, CAS NO. 24979-70-2. The phenolic resin was BB-139 from Reichhold Chemicals. The poly(ethylene oxide) was from Polysciences, Inc., Warrington, Pa. In Table 3, the PEO was either Polyox 301, MW 4,000,000 or Polyox 303, MW 7,000,000, both from Union Carbide Corporation and the furnish was otherwise the same as that in Table 2. 
     
                                           TABLE 1__________________________________________________________________________A furnish consisting of 85% chemi-thermomechanical pulp and 15%kraft pulp with 20 pounds of alum per ton from a newsprint mill wastested in aPDDT at 0.48% consistency with the following results:  Pounds per ton:  poly(paravinyl     Pounds per ton:             Pounds per ton: Drainage TimepH  phenol) Phenolic Resin             PEO     Fines Retention                             Secs. to 100 ml.__________________________________________________________________________4 0       0.8     0.2     2.54%   174 0       0.8     0.4     12.87   174 0       0.8     0.8     26.06   194 0       0.8     1.0     19.03   184 0.8     0       0.2     7.5     194 0.8     0       0.4     16.60   194 0.8     0       0.8     24.75   184 0.8     0       1.0     32.09   164 0       1.2     0.2     7.34    174 0       1.2     0.4     17.34   164 0       1.2     0.8     17.25   154 0       1.2     1.0     24.70   164 1.2     0       0.2     5.36    174 1.2     0       0.4     13.76   174 1.2     0       0.8     29.10   174 1.2     0       1.0     35.06   155 0       0.8     0.2     8.05    205 0       0.8     0.4     18.70   205 0       0.8     0.8     41.09   175 0       0.8     1.0     49.10   165 0.8     0       0.2     18.06   205 0.8     0       0.4     35.54   185 0.8     0       0.8     57.29   145 0.8     0       1.0     58.29   125 0       1.2     0.2     5.36    195 0       1.2     0.4     23.70   185 0       1.2     0.8     40.45   165 0       1.2     1.0     49.73   155 1.2     0       0.2     17.45   215 1.2     0       0.4     30.85   185 1.2     0       0.8     61.41   145 1.2     0       1.0     64.85   13__________________________________________________________________________ 
    
     
                                           TABLE 2__________________________________________________________________________A furnish of 72% Thermomechanical pulp and 28% kraft pulp wasobtained from a paper mill and tested in the PDDT with the followingresults:  Pounds per ton:  poly(paravinyl     Pounds per ton:             Pounds per ton: Drainage TimepH  phenol) Phenolic Resin             PEO     Fines Retention                             Secs. to 100 ml.__________________________________________________________________________4 0       0.8     0.2     -1.29%  184 0       0.8     0.4     -2.47   174 0       0.8     0.8     -2.33   174 0       0.8     1.0     1.06    184 0.8     0       0.2     4.14    174 0.8     0       0.4     10.12   164 0.8     0       0.8     22.34   164 0.8     0       1.0     32.76   154 0       1.2     0.2     -2.92   184 0       1.2     0.4     1.31    194 0       1.2     0.8     4.84    194 0       1.2     1.0     7.88    194 1.2     0       0.2     4.78    174 1.2     0       0.4     12.67   164 1.2     0       0.8     26.40   164 1.2     0       1.0     27.54   155 0       0.8     0.2     -0.51   195 0       0.8     0.4     38.94   165 0       0.8     0.8     45.90   165 0       0.8     1.0     62.03   145 0.8     0       0.2     11.11   195 0.8     0       0.4     21.87   195 0.8     0       0.8     46.54   155 0.8     0       1.0     59.04   135 0       1.2     0.2     7.86    185 0       1.2     0.4     28.00   195 0       1.2     0.8     62.54   135 0       1.2     1.0     62.70   125 1.2     0       0.2     9.42    205 1.2     0       0.4     18.52   205 1.2     0       0.8     49.47   165 1.2     0       1.0     53.89   14__________________________________________________________________________ 
    
     
                                           TABLE 3__________________________________________________________________________A furnish of 72% Thermomechanical pulp and 28% kraft pulp wasobtained from a paper mill and tested in the PDDT with the followingresults:  Pounds per ton:  poly(paravinyl     Pounds per ton:             Pounds per ton: Drainage TimepH  phenol) Phenolic Resin             PEO     Fines Retention                             Secs. to 100 ml.__________________________________________________________________________5.1  0       0.26    *0.51   16.92   545.1  0       0.51    *0.51   47.40   345.1  0       1.04    *0.52   63.19   185.1  0       1.54    *0.51   65.85   175.1  0       1.98    *0.49   51.02   265.1  0.27    0       *0.53   10.30   585.1  0.51    0       *0.51   25.23   485.1  1.03    0       *0.52   68.34    95.1  1.54    0       *0.51   63.62   145.1  2.04    0       *0.51   56.35   145.1  0.52    0       **0.52  28.41   465.1  1       0       **0.5   80.33    95.1  1.49    0       **0.5   60.41   225.1  1.98    0       **0.49  48.34   165.1  0       0.5     **0.5   33.80   445.1  0       1       **0.5   52.56   265.1  0       1.54    **0.51  58.00   195.1  0       1.97    **0.49  56.70   23__________________________________________________________________________ *Polyox 303 from Union Carbide Corp. **Polyox 301 from Union Carbide Corp. 
    
     Two additional samples of poly(paravinylphenol) were used in the process according to the invention as follows: (1) Poly(paravinylphenol) from Maruzen Petrochemical Co., LTD., &#34;Maruka Lyncur M&#34;, Grade S-2, CAS NO. 24979-70-2, Weight Avg. Molecular weight (manufacturer&#39;s data): 5,200; and (2) Poly(paravinylphenol) from Maruzen Petrochemical Co., LTD., &#34;Maruka Lyncur M&#34;, Grade H-2, CAS NO. 24979-70-2, Weight Avg. Molecular weight (manufacturer&#39;s data): 23,000. 
     The resins were tested for performance together with Union Carbide Polyox 301 polyethyleneoxide for retention of fine particles in a newsprint pulp sample of 85% CTMP pulp and 15% kraft pulp. The comparison was done with 0.045 to 0.05% polyethylene oxide by weight of the pulp furnish. The Reichold BB-139 phenol formaldehyde resin is included for comparison. 
     
                                           TABLE 4__________________________________________________________________________COMPARISON OF HIGH AND LOW MOLECULAR WEIGHTPOLYPARAVINYL PHENOL PER CENT FINES RETENTIONMaruzen Maruzen       Maruzen             Maruzen                   Reichold                         ReicholdGrade S-2 Grade S-2       Grade H-2             Grade H-2                   BB-139                         BB-139Ratio of %     Ratio of             %     Ratio of                         %phenolic/ Fines phenolic/             Fines phenolic/                         FinesPEO   retention       PEO   retention                   PEO   Retention__________________________________________________________________________0.51  58.56 0.51  60.58 0.5   30.871.0   75.73 1.0   77.71 1.0   50.651.5   74.70 1.51  77.41 1.49  54.422.0   75.25 2.0   73.76 --    --3.01  60.33 3.01  56.97 --    --3.98  43.06 3.98  52.17 --    --__________________________________________________________________________ 
    
     The data shows that at low ratios of poly(paravinyl-phenol) to PEO, there is an advantage for the higher molecular weight material for fines retention. 
     
                                           TABLE 5__________________________________________________________________________COMPARISON OF HIGH AND LOW MOLECULAR WEIGHTPOLYPARAVINYL PHENOL DRAINAGE TIME TO 100 ML.Maruzen Maruzen       Maruzen             Maruzen                   Reichold                         ReicholdGrade S-2 Grade S-2       Grade H-2             Grade H-2                   BB-139                         BB-139Ratio of Drainage,       Ratio of             Drainage,                   Ratio of                         Drainage,phenolic/ Seconds to       phenolic/             Seconds to                   phenolic/                         Seconds toPEO   100 ml.       PEO   100 ml.                   PEO   100 ml.__________________________________________________________________________0.51  16    0.51  12    0.5   111.0   13    1.0    9    1.0   111.5   14    1.51   9    1.49  122.0   13    2.0   15    --    --3.01  13    3.01  16    --    --3.98  14    3.98  15    --    --__________________________________________________________________________ 
    
     There is an advantage for the higher molecular weight material for more rapid drainage. 
     Thus it has been shown that poly(paravinyl phenol) is an effective substitute for phenol-formaldehyde resin and that under some circumstances performs more effectively on a pound for pound basis: as the pH is lowered from 5 to 4 the poly(paravinyl phenol)is consistently more effective than the phenolformaldehyde resin. The additional advantage of the poly(paravinyl phenol) is that it contains no formaldehyde.