Abstract:
An improved process for melt cutting ethylene polymers is provided wherein the improvement comprises adding to the melt cutter water a small amount of nonionic or anionic surfactants thereby significantly increasing the agglomeration temperature of the ethylene polymer. This allows for an increase in melt cutting capacity and productivity.

Description:
This is a continuation of application Ser. No. 010,047, filed Feb. 6, 1979 now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to melt cutting and more specifically it relates to an improved process for the melt cutting of ethylene polymers. 
     2. Description of the Prior Art 
     The use of surfactants is wide spread in many applications. For example, ethylene oxide and propylene oxide copolymer surfactants are disclosed in U.S. Pat. Nos. 3,422,049, and 3,432,483, as aiding the preparation of dispersions of polymers with particle sizes of below 10 microns to not greater than 25 microns and in U.S. Pat. No. 4,007,247 for the preparation of fibrils, i.e., short fibers having diameters less than 25 microns and preferably less than 10 microns. All three of these patents disclose water dispersion processes for polymer particle size reduction using high temperatures and pressures as well as high speed agitation and surfactants. 
     U.S. Pat. No. 3,528,841 deals with reducing the tackiness of polymer pellets by applying a small particle size (less than 10 microns) polyolefin powder dispersed in water on the surface of the soft, sticky polymer to reduce its tackiness. In the alternative, the polyolefin powder coating can also be applied to the polymer by tumbling or by airveying. The purpose of applying this coating is to facilitate getting the product through the drying and purge steps of the production process and to supply a free flowing product to the trade. 
     Chemical Abstracts digest 87:153195p, Vol. 87, 1977 p. 48, entitled &#34;Agglomeration prevention during stream-stripping of solvents from rubber solutions&#34; involves the use of a 1000-3000 molecular weight ethylene oxide/propylene oxide copolymer as a surfactant in a water/hydrocarbon solvent dispersion. Thus, a 20% solids butadiene rubber solution in hexane was steam-stripped in a 0.005 weight percent solution of the above surfactant in water. This mixture forms a dispersion (oil in water at about 5 to 6% solids) and establishes the particle size of the rubber crumbs (average diameter 3.7 mm). The surfactant&#39;s function is to make the two imcompatible phases, namely, hexane and water into one compatible phase. Steam stripping is used to obtain a single liquid (water) phase, ending up with an 8% solids slurry. The process involves forming a particle size in dispersion form from a solution of the rubber in a hydrocarbon solvent. 
     SUMMARY OF THE INVENTION 
     According to the present invention there is provided an improved process for melt cutting ethylene polymers, which process comprises extruding the molten thermoplastic polymer through one or more orifices into water and cutting the extruded strand as it undergoes solidification, wherein the improvement comprises adding to the water from about 1 to about 1000 ppm by weight of at least one surfactant selected from the group consisting of non-ionic and anionic surfactants that will increase by at least 10° C. the agglomeration temperature of an ethylene polymer that has an agglomeration temperature of from about 50° C. to about 60° C., said surfactant having a hydrophilic/lipophilic balance (HLB) range of from about 10 to about 45. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Surprisingly it was found that the addition of small quantities of a non-ionic surfactant to the melt cutter water significantly increased the agglomeration temperature of soft ethylene/vinyl acetate copolymers. In the context of the present invention, the term &#34;agglomeration temperature&#34; means the agglomeration temperature of extruded, hot, cut pellets in water. Agglomeration temperature is determined by the process described below under &#34;Laboratory Testing Procedure&#34;. This increase in the agglomeration temperature results in an increase in melt cutting capacity and productivity. 
     Surfactants that are contemplated for use by the present invention are non-ionic and anionic surfactants that will increase by at least 10° C. the agglomeration temperature of an ethylene polymer that has an agglomeration temperature of from about 50° C. to about 60° C. Suitable surfactants have a hydrophilic/lipophilic balance (HLB) range of from about 10 to about 50. 
     Non-ionic surfactants are preferred and the preferred class of non-ionic surfactants are homo- and copolymers of olefin oxides wherein the olefin moiety contains up to 3 carbon atoms, such as ethylene and propylene oxide homo- and copolymers. The preferred (HLB) range is from about 20 to about 35. 
     A high molecular weight &#34;Pluronic&#34; polyol, an α-hydro-omega-hydroxy-poly(oxyethylene) poly(oxypropylene) poly(oxyethylene) block copolymer with an HLB range of about 10 to about 35 is the most preferred surfactant. Other non-ionic surfactants, however, such as oxyethylated straight chain alcohols, octyl phenoxy polyethoxy ethanol, ethylene oxide polymers and a reverse &#34;Pluronic&#34; 25-R-8 [poly(oxypropylene)-poly(oxyethylene)-poly(oxypropylene) block copolymer] also significantly raised the agglomeration temperature of ethylene polymers in water. 
     At essentially equivalent HLB values the higher molecular weight polymers appear to be most effective. 
     The range of concentration for the melt cutter additive surfactant of the present invention is from about 1 to about 1000 parts per million (ppm) based upon the weight of the melt cutter water. The preferred range for the more effective surfactants is from about 1 to about 100 ppm. 
     Although the increased agglomeration temperature obtained by the process of the present invention was discussed in terms of ethylene/vinyl acetate (EVA) copolymers it is to be understood that the present invention applies to other soft ethylene polymers as well where tackiness and agglomeration are of concern. 
     It is very important in the manufacture of polymers used in adhesives that the concentration of additives used in processing these polymers be as low as possible so as not to result in an adverse effect on critical adhesive properties. As illustrated below in the examples, surfactants of the present invention show no adverse affect on adhesion in the critical adhesion to aluminum test at concentrations of 20 ppm, as well as even up to 2000 ppm in some instances. 
     Illustrative examples of commercially available surfactants are &#34;Pluronic&#34; F-98, &#34;Pluronic&#34; F-108, &#34;Plurafac&#34; A-38, &#34;Pluronic&#34; F-38, &#34;Pluronic&#34; 25R-8, &#34;Sipon&#34; L-22, &#34;Carbowax&#34; 20 M, &#34;Pluronic&#34; P-104, &#34;Triton&#34; X-100. 
    
    
     The following examples are given for the purpose of illustrating the present invention. All parts and percentages are by weight unless otherwise specified. 
     LABORATORY TESTING PROCEDURE 
     These tests were made using a 10/1 water/polymer ratio. Ethylene/vinyl acetate copolymer pellets were agitated in ambient temperature water using mild paddle-type agitation that will assure the movement of pellets in the water. The temperature of the water was gradually increased until significant agglomeration had occurred. In the case of untreated Elvax® 210, the first indication of tackiness occurred at approximately 50° C. (3 to 5 pellets agglomeration around the thermometer and agitator shaft). The second indicator was larger agglomerates (1/4&#34; to 1/2&#34;) forming at a temperature of 54° C. The third and final indicator was significant agglomeration (large clump 1&#34; to 2&#34; in diameter) occurring at a temperature of 58° C. This is the temperature considered as the agglomeration temperature of Elvax® 210. In this study, the various melt-cutter additives were dissolved in the water prior to adding the ethylene/vinyl acetate copolymer pellets. 
     EXAMPLE 1 
     This example demonstrates the effect of &#34;Carbowax&#34; 20 M, a very slightly crosslinked ethylene oxide copolymer (for further characterization see Table I), as a melt-cutter additive in laboratory tests to increase the agglomeration temperature of soft polymer grades of EVA [e.g., Elvax® 40, (40% VA, 57 M.I.), Elvax®, 150 (33% VA, 43 M.I.) and Elvax® 210 (28% VA, 400 M.I.)]. These tests were merely scouting tests without full attention being paid to the adequacy of agitation required to assure submersion of the pellets in the surfactant containing water. Accordingly the results are merely a rough indication of the effect of the surfactant. The tests involved the addition of 2500 ppm of &#34;Carbowax&#34; 20 M (based on the weight of the water) agitated with a magnetic stirrer. No agglomeration occurred at 70° C. for Elvax® 40 and and 150. Pellets of Elvax® 210 were about 60% agglomerated at 70° C. Additional tests were run using Elvax® 40 at 1250 and 500 ppm based on the water, and these tests showed no agglomeration up to 70° C. 
     EXAMPLE 2 
     This example demonstrates the effect of &#34;Pluronic&#34; F-98 and F-108, ethylene oxide-propylene oxide-ethylene oxide block copolymers (for further characterization see Table I), as melt-cutter additives in laboratory tests to increase the agglomeration temperature of soft polymer grades of EVA (such as, Elvax® 210). Following the same procedure described under Laboratory Testing Procedure, the following results were obtained: 
     
         ______________________________________       Melt-Cutter    AgglomerationMelt-Cutter Additive       TemperatureAdditive    (ppm based on H.sub.2 O)                      (°C.)______________________________________Control     0              58&#34;Pluronic&#34;  0.5            65F-98&#34;Pluronic&#34;  1.0            71F-98&#34;Pluronic&#34;  2.0            87F-98&#34;Pluronic&#34;  10.0           94F-98&#34;Pluronic&#34;F-108       0.5            65F-108       1.0            70F-108       2.0            88F-108       10.0           94______________________________________ 
    
     EXAMPLES 3-6 AND COMPARATIVE EXAMPLES 1-9 
     These examples represent the evaluation of samples from various classes of surfactants (e.g., nonionic, anionic, and cationic) in the laboratory melt-cutting study on Elvax® 40, 150 and 210. The results are shown in Tables I and II. 
     
                       TABLE I______________________________________EFFECT OF MELT-CUTTER ADDITIVES ONAGGLOMERATION TEMPERATURE OF ELVAX® 210______________________________________                                  Sur-                                  face                                  Ten-                                  sion                                  Dynes/Ex-                                    Cm.am-  Melt-Cutter         Chemical      0.1%.sup.(3),ples Additive            Composition   25° C.______________________________________No AdditiveC1   (Control)           --            --3    &#34;Pluronic&#34; F-108    α hydro-omega-                                  41.24    &#34;Pluronic&#34; F-98     hydroxy-poly- 43.0                    (oxymethylene)5    &#34;Pluronic&#34; F-38     poly(oxypropylene) poly                                  52.26    &#34;Pluronic&#34; P-104    (oxyethylene) block                                  33.1  7.sup.(5)&#34;Pluronic&#34; L-121.sup.(2)                    copolymer     39.6C2   &#34;Pluronic&#34; L-43                   47.38    &#34;Plurafac&#34; A-38     Oxyethylated                    Straight Chain                    Alcohol       43.69    &#34;Triton&#34; X-100      Octylphenoxy-                    polyethoxy                    ethanol       31.010   &#34;Carbowax&#34; 20M      Very slightly crosslinked                    ethylene oxide polymer                                  52.0 @                                  50%                                  by Wt.11   &#34;Pluronic&#34;  25R-8   α hydro-omega-hydroxy-                    poly(oxypropylene) poly                    (oxyethylene) poly(oxy-                    propylene) block                    copolymer     46.1C3   &#34;Polyox&#34; WSRN-10C4   &#34;Polyox&#34; WSRN-750   More highly crosslinkedC5   &#34;Polyox&#34; WSR-205    ethylene oxide copolymerC6   &#34;Polyox&#34; WSR-110512   &#34;Sipon&#34; L-22        Ammonium Salt of Lauryl                    SulfateC7   &#34;Atlas&#34; G-263       n-cetyl-n-ethyl morpho-                    lineum______________________________________                            95° C. Agglomera-                            tion Tempera-  Surfactant            HLR     Average ture.sup.(1) (ppmExamples  Type      Factor  Mol. Wt.                            Based on Water)______________________________________C1     --        --      --      Agglomerates @                            58° C.3      Nonionic  27.0    14,000   134      Nonionic  27.5    13,500   135      Nonionic  30.5    5,000    306      Nonionic  13.0    5,850    307      Nonionic  0.5.sup.(5)                    4,400   75° C. @ 1000 ppmC2     Nonionic  13.5    1,850   67° C. @ 1000 ppm8      Nonionic  20      1,420    389      Nonionic  13.5    628     29510     Nonionic  20      14,000- 440                    20,00011     Nonionic  30.3    9,000   465C3     Nonionic  20      100,000 62° C. @ 1000 ppmC4     Nonionic  20      300,000 63° C. @ 1000 ppmC5     Nonionic  20      600,000 63° C. @ 1000 ppmC6     Nonionic  20      900,000 63° C. @ 1000 ppm12     Anionic   31      --      875C7     Cationic  30      --      66° C. @ 1000 ppm______________________________________Agglomeration Temperature (°C.) atIndicated Surfactant Level (ppm).sup.(4)Ex.  0       0.5     1.0   2.0   2.5   5     10  20______________________________________C1   58      --      --    --    --    --    --  --3    58      65      70    88    --    --    94  --4    58      65      71    87    --    --    94  --5    58      --      --    --    --    --    62  686    58      --      --    --    --    67    90  --C2   58      --      --    --    --    --    --  -- 7   58      Insoluble in Water.sup.(5)8    58      --      65    --    --    --    68  919    58      --      --    --    --    --    --  --10   58      --      --    --    --    --    --  6311   58      --      --    --    --    63    --  --12   58      --      --    --    --    61    --  --C3   58      60      60    62    --    --    62  --C4   58      62      63    63    --    --    63  --C5   58      63      63    63    --    --    63  --C6   58      63      63    63    --    --    63  --C7   58      --      --    --    --    63    --  --______________________________________Agglomeration Temperature (°C.) atIndicated Surfactant Level (ppm).sup.(4)Ex.  30      40     50   100   200   300   500  1000______________________________________C1   --      --     --   --    --    --    --   --3    --      --     --   --    --    --    --   --4    --      --     --   --    --    --    --   --5    &gt;97     --     --   --    --    --    --   --6    --      --     --   &gt;97   --    --    &gt;97  &gt;97C2   --      --     --   65    --    --    67   677    Insoluble in Water.sup.(5)8    --      --     --   --    --    --    --   --9    --      --     --   65    69    &gt;97   --   --10   --      --     77   84    --    --    &gt;97  --11   --      --     67   70    79    --    &gt;97  --12   --      --     61   --    --    --    67   &gt;97C3   --      --     --   --    --    --    --   60C4   --      --     --   --    --    --    --   60C5   --      --     --   --    --    --    --   61C6   --      --     --   --    --    --    --   64C7   --      --     63   --    --    --    65   66______________________________________ .sup.(1) except where indicated otherwise .sup.(2) limited solubility in water .sup.(3) wt. % concentration .sup.(4) based on water .sup.(5) not an example of the present invention, HLB factor = 0.5, insoluble in water 
    
     
                       TABLE II______________________________________Effect Of Melt-Cutter Additives On AgglomerationTemperature Of Elvax® 40 and 150Agglomeration Temperature (°C.)at indicated surfactant level (ppm).sup.(1)Ex.  Additive  0      0.5 1.0  2.0 2.5   5    10   20______________________________________C8   None      45     --  --   --  --    --   --   --C9   None      55     --  --   --  --    --   --   --13   &#34;Pluronic&#34;F-98      45     --  --   --  --    --   --   --14   &#34;Pluronic&#34;F-98      55     --  --   --  &gt;85   &gt;85  --   --15   &#34;Pluronic&#34;F-108     45     --  --   --  --    --   --   --16   &#34;Pluronic&#34;F-108     55     --  --   --   90   --   92   --______________________________________Effect Of Melt-Cutter Additives On AgglomerationAgglomeration Temperature (°C.)at indicated surfactant level (ppm).sup.(1)Ex.   30     40     50   100    200 300   500  1000______________________________________C8    --     --     --   --    --   --    --   --C9    --     --     --   --    --   --    --   --13    --     --     &gt;85  --    --   --    --   --14    --     --     --   --    --   --    --   --15    --     --      96  --    --   --    --   --16    --     --     &gt;95  --    --   --    --   --______________________________________ .sup.(1) based on water 
    
     EXAMPLES 17-22 
     The effect of the concentration of &#34;Pluronic&#34; F-98 in the melt-cutter water on the adhesive properties of Elvax® 40 to aluminum foil was studied. The results summarized in Table III show that up to and including 2,000 ppm of additive (based on the water) had little or no effect on adhesion properties. 
     EXAMPLE 23 AND COMPARATIVE EXAMPLE 10 
     The use of 20 ppm &#34;Pluronic&#34; F-98 as a melt-cutter additive was evaluated on a commercial scale in a continuous melt-cutter process for making one of the slower cutting grades of polymer, Elvax® 210. This resulted in nearly a 50% increase in melt-cutting rates. This product, as well as a control product of Elvax® 210, was evaluated for color, odor, gel content, and adhesion to aluminum foil, both as is and after aging. The results were summarized in Table IV. &#34;Pluronic&#34; F-98 melt-cutter additive had no adverse effect on any of the above properties. 
     ESCA (electron spectroscopy for chemical analysis) determination of the above Elvax® 210 processed using 20 ppm &#34;Pluronic&#34; F-98 based on the melt-cutter water show 0.12 ppm surfactant on the polymer pellets on an 80% confidence level or 0.34 ppm based on 95% confidence level. 
     EXAMPLES 24-27 AND COMPARATIVE EXAMPLES 11-14 
     These examples show the effect of nonionic melt cutter additives on the agglomeration temperature of four soft ethylene terpolymer resins. The tests were run according to the Laboratory Testing Procedure described above. The data, summarized in Table V, show for the first three polymers that the addition of a nonionic surfactant (Pluronic® F-98), at a concentration of 20 parts per million (ppm) based on the water, significantly increased their agglomeration temperature. For the fourth polymer, E/MA/MAME, 50 ppm Pluronic® F-108 based on the water, significantly increased the agglomeration temperature of this terpolymer. 
     
                       TABLE III______________________________________EFFECT OF CONCENTRATION OF&#34;PLURONIC&#34; F-98 ON ADHESIVEPROPERTIES OF ELVAX® 40      Peel Strength Data (lbs./inch)Melt-      Heat Seal, 5-Mil Aluminum.sup.(2)Cutter     248° F. 350° F. Additive         Std.           Std.Ex.   ppm.sup.(1)          Peel    Deviation                           Peel  Deviation______________________________________C10   0        3.45    0.17     6.1   1.0617    5        2.75    0.53     3.85  0.2318    10       2.9     0.60     4.5   0.8619    20       3.58    0.36     4.83  0.3320    200      3.1     0.16     4.38  0.2121    2,000    3.65    0.10     4.68  0.3122    20,000   0.75    0.31     1.48  0.13______________________________________ .sup.(1) Based on meltcutter water. .sup.(2) Heat Seal Conditions: Pressure = 20 psi; Dwell Time = 6 seconds each side. 
    
     
                       TABLE IV______________________________________        Example                   23        C-10       20 ppm        No Additive                   &#34;Pluronic&#34; F-98______________________________________Pellet Appearance          Normal       NormalPeel Strength.sup.(1), lbs./in.InitialSealing Temp. 120° C.          .47          .46Sealing Temp. 177° C.          3.8          5.3Aged 1 WeekSealing Temp. 120° C.          .43          .73Sealing Temp. 177° C.          4.0          3.6______________________________________ .sup.(1) Sealed to aluminum foil 6 seconds, 20 psi. 
    
     
                       TABLE V______________________________________EFFECT OF &#34;PLURONIC&#34; F-98 &amp; F-108MELT-CUTTER ADDITIVES ON THE AGGLOMERATIONTEMPERATURE OF ETHYLENE POLYMERS                            Melt-                            Cutter                       Melt Additive                                    Agg.             Compo-    In-  (ppm based                                    Temp.Ex.  Polymer      sition    dex  on water)                                    (°C.)______________________________________C11  E/VA/CO.sup.(3)             61/29/10  35   0       5224   E/VA/CO.sup.(3)             61/29/10  35   20 (F-98)                                    93C12  E/VA/MAA.sup.(4)             74/25/1   500  0       6225   E/VA/MAA.sup.(4)             74/25/1   500  20 (F-98)                                    92C13  E/MA/CO.sup.(1)             64.2/22.7/                       81   0       60             13.126   E/MA/CO.sup.(1)             64.2/22.7/                       81   20 (F-98)                                    95             13.1C14  E/MA/MAME.sup.(2)             43/53/4    9   0       6127   E/MA/MAME.sup.(2)             43/53/4    9    50 (F-108)                                    97______________________________________ .sup.(1) Ethylene/methyl acrylate/carbon monoxide copolymer. .sup.(2) Ethylene/methyl acrylate/monoethylester of maleic acid copolymer .sup.(3) Ethylene/vinyl acetate/carbon monoxide copolymer. .sup.(4) Ethylene/vinyl acetate/methacrylic acid copolymer. 
    
     Agglomeration temperatures of various Elvax® grades are indicated on Table VI below. 
     
                       TABLE VI______________________________________Agglomeration Temperature of Elvax® Grades                          AgglomerationElvax®   Melt Index             Vinyl Acetate %                          Temperature (°C.)______________________________________ 40     57        40           45150     43        33           55210     402       28           58250     25        28           67260     6         28           64265     3         28           76310     402       25           59350     19.1      25           65360     2         25           72410     502       18           63420     150       18           72460     2.5       18           81______________________________________