Abstract:
A certain class of poly(ester-amide) polymers are disclosed which are particularly suitable as hot melt adhesive compositions particularly advantageous for bonding plastics, such as polyester or polycarbonate polymers. The particular class of poly(ester-amides) are those which include a polymeric fat acid, and more specifically a dimeric fat acid component, in which the ester segments will contribute from about 20, preferably 35 to about 60 weight percent of the poly(ester-amide) and the amide segment contributing the remainder.

Description:
This is a division of application Ser. No. 742,254, filed June 7, 1985, now U.S. Pat. No. 4,656,242, issued Apr. 7, 1987. 
    
    
     This invention relates to a certain class of poly(ester-amide) polymers which are particularly suitable as hot melt adhesive compositions particularly advantageous for bonding plastics, such as polyester or polycarbonate polymers. The particular class of poly(ester-amides) are those which include a polymeric fat acid and more specifically a dimeric fat acid component in which the ester segments will contribute from about 20, preferably 35 to about 60 weight percent of the poly(ester-amide) and the amide segment contributing the remainder. 
     BACKGROUND OF THE INVENTION 
     Poly(ester-amide) adhesive compositions have been known for some time in the art, including the use as hot melt adhesives for various substrates such as metals, wood and plastics. Included in this background of poly(ester-amide) compositions are U.S. Pat. Nos. 3,650,999, 4,343,743, and 4,485,233. Each of these three patents may include a polymeric fat acid component. U.S. Pat. No. 3,650,999, related to poly(ester-amide) compositions, is generally useful as adhesives to a variety of substrates such as steel, aluminum, wood and plastic substrates. By the proper selection of reactants and using special polymerization techniques, a block copolymer poly(ester-amide) composition was prepared having certain advantages in high temperature properties over earlier adhesive compositions. However, the products do not possess good low temperature properties. The block copolymer is a composition comprising from 30 to 70% by weight crystalline polyester segments and 70 to 30% of amorphous polyamide segments. The polyesters employed were high melting crystalline polyesters of aromatic acids and glycols and copolyesters thereof, which provided polyester segments having melting points in the range of 180° to 270° C. 
     U.S. Pat. No. 4,343,743 deals with copoly(ester-amides) having a random, alternately or regularly recurring block structure in which the improvement over U.S. Pat. No. 3,650,999 is alleged as providing products having a glass transition temperature below -30° C. so that the polymers remain pliable down to temperatures of that level. However, the products do not possess good heat fail properties. As disclosed in this patent, the proportion by weight of polyester segments is preferably between 50 and 80% by weight although a general range of 20 to 80% is disclosed. 
     U.S. Pat. No. 4,485,233 relates to poly(ester-amide) compositions which include a polymeric fat acid component and which are indicated as employing diamines and diols which contain a high proportion of non-hydrogen bonding groups or an odd number of carbon atoms to provide advantageous crystallization properties which permit long open assembly times. Within the general requirement that substantially equivalent amounts of carboxyl and amine groups be present in the reaction mixture provide a neutral or balanced poly(ester-amide), the proportions of the reactants are 10 to 60 equivalent percent of the polymeric fatty acid, 40 to 90 equivalent percent of another dicarboxylic acid, 40 to 90 equivalent percent of a diamine and 10 to 60 equivalent percent of a diol. 
     SUMMARY OF THE INVENTION 
     It has been discovered that a particular class of poly(ester-amide) compositions employing a polymeric fat acid component have particularly good adhesive properties, especially in relation to the bonding of plastics such as polyesters or polycarbonates, and in particular where such substrates are required to be bonded to metals particularly protected metals, such as tinplate and galvanized steel. Thus the poly(ester-amides) of the present invention are particularly useful in trilamination of polyester materials to aluminum such as a Mylar/aluminum/Mylar laminate. Further the products are particularly useful in bonding polycarbonate aerodynamic headlamps for automobiles. 
     The products of this invention possess an overall desirable combination of both high and low temperature properties in addition to their advantageous adhesive properties. The most desirable products of this invention will possess a Ball and Ring softening point greater than about 150° C., a heat fail temperature of greater than 120° C. and a flexibility such as to pass a 1/8&#34; mandrell at -20° F. 
     The poly(ester-amides) of this invention which find utility in the above noted application areas are those generally using the proportions and amounts of reactants found in the earlier references noted above with the amounts, however, being so selected and adjusted so as to provide a final poly(ester-amide) polymer having from about about 20, preferably 35 to about 60 weight percent polyester segments based on the total weight of polymer with the remainder being the amide segments. The products is preferably a random copolymer prepared under the usual condensation reaction conditions for preparation of poly(ester-amides) by reacting an acid component comprising: 
     (a) from 10 to 80 and preferably to 60 equivalent percent of the polymeric fat acid, and 
     (b) from 20, preferably 40, to 90 equivalent percent of a linear dicarboxylic acid; 
     with a substantially equivalent amount of an amine and diol component comprising 
     (c) from 40 to about 90, and preferably 50-80 equivalent percent of an organic diamine and 
     (d) 10, or preferably 40, to 60 equivalent percent of a diol. 
     DETAILED DESCRIPTION OF THE INVENTION 
     As indicated above, the poly(ester-amide) compositions of this invention are prepared from the reactants noted using the amounts and adjusting the proportions of the reactants so as to provide a final polymer in which the polyester segments comprise from about 20, preferably 35 to about 60 weight percent of the total weight of polymer with the polyamide forming of the balance of the polymer. The reactants employed to prepare the poly(ester-amide) compositions of the invention are old and well known as are the methods preparation of the poly(ester-amide) compositions. The techniques and general method of forming the polymer are the usual condensation reaction conditions for forming polyamides. In general these conditions are reaction at temperatures at about 100° to 300° C. for a sufficient time to effect poly(ester-amide) formation. In general the reactions may be initially heated to a temperature of about 125° or 130° to 150° or 160° C. to initiate polymerization and thereafter at higher temperatures sufficient to distill off the water of condensation. Illustrative of such higher temperatures are temperatures of about 200-250 and quite generally 210°-235° C. The reaction is generally carried out by charging the resin reactor kettle with the reactants in the proportions desired and heating to the temperature at which random polymerization occurs. Random polymerization occurs by charging all of the reactants at one time in contrast to block polymerization in which case at least one and preferably both the polyester and polyamides are preformed and subsequently reacted with the other polymer or the corresponding reactants. The products of the present invention may be random polymers or block copolymers. In some cases the block copolymers provide a more desirable combination of high temperature properties associated with low temperature properties. 
     The polymeric fatty or fat acids also sometimes referred to in the art as &#34;dimer acids&#34; are products resulting from the polymerization of fatty acids. The polymeric fat acids are well known and a summary of the preparation of such acids is found in U.S. Pat. No. 3,157,681. Commercially available polymeric fat acids generally are prepared from polymerization of tall oil fatty acids which will generally have a composition as follows: 
     
         ______________________________________               Percent by Weight______________________________________C.sub.18 monobasic acids (monomer)                  5-15C.sub.36 dibasic acids (dimer)                 60-80C.sub.54 and higher polybasic acids (trimer)                 10-35______________________________________ 
    
     Polymeric fat acids having a higher dimeric fat acid content in excess of 65% by weight and preferably in excess of 90 or 95% by weight are obtained by fractionation by suitable means such as high vacuum distillation to provide very high purity products having a dimeric fat acid content in the order of 98-99%. There will be less than 1% monomer and/or trimer. 
     A more detailed description and summary of the preparation of polymeric fat acids can be found in U.S. Pat. No. 3,377,303 and the description therein is incorporated herein by reference. 
     A wide variety of dicarboxylic acids may also be employed along with the polymeric fat acids and the preparation of a compositions of this invention. The dicarboxylic compounds employed in the present invention are the aliphatic or cycloaliphatic hydrocarbon compounds, preferably those of the formula: 
     
         ROOC--COOR or ROOCR.sub.1 COOR 
    
     where R is selected from the group consisting of hydrogen or alkyl groups containing from 1-8 carbon atoms and R 1  is a divalent aliphatic hydrocarbon (preferably straight chain), or cycloaliphatic, radical having from 1 to 20 and preferably 4 to 12 carbon atoms. The preferred esters are the alkyl esters having from 1-4 carbon atoms, the most preferred being the methyl or ethyl esters. The dicarboxylic acids preferably are those containing at least 6 carbon atoms up to about 12 carbon atoms. Illustrative of the dicarboxylic compounds are oxalic, malonic, glutaric, adipic, succinic, suberic, azelaic, sebacic, dodecanedioic and pimelic acids. Such dicarboxylic acids are well known, readily available commercially, with adipic, azelaic and sebacic the most common. 
     The organic diamines, which are employed in the present invention, are preferably the aliphatic or cycloaliphatic diamines having from about 2 to 20 carbon atoms. Especially preferred are the alkylene diamines, such as ethylene diamine, diaminopropane, diaminobutane, and hexamethylene diamine. Ideally, these preferred diamines are represented by the formula H 2  NR 2  NH 2  where R 2  is an aliphatic, (preferably straight chain) or cycloaliphatic hydrocarbon radical having from 2-20 carbon atoms. Heterocyclic diamines such as piperazine may also be employed. The most preferred of the alkylene diamines is hexamethylene diamine which provides the most desirable overall combination of properties. 
     Diols employed in the invention are also generally well known compounds also available commercially. Representative of the preferred diols are the straight chain aliphatic, or cycloaliphatic diols having from 2-20, and preferably 2-6 carbon atoms such as ethylene glycol, 1,3-propylene glycol, 1,4-butylene glycol, neopentyl glycol and 1,6-hexamethylene glycol. These may be ideally represented by the formula HOR 1  OH where R 1  is as earlier defined. Ether diols such as polyoxyethylene glycol may be employed in which one R 1  will also contain an oxygen atom. 
     The following examples will serve to best illustrate the spirit and scope of the present invention. These examples are not to be construed as limiting, but illustrations of the invention. Percentages and parts are by weight unless otherwise indicated. Also for convenience and illustration, the polymeric fat or fatty acid employed in the examples are polymerized tall oil fatty acids except where otherwise noted. 
    
    
     EXAMPLES 
     Example 1 
     Typical Preparation Procedure 
     The reactants are placed in the reactor which is sealed and a nitrogen sweep is employed to remove any air as heating and stirring begin. Venting is begun when the pressure reaches about 100-120 psig. or when temperature reaches 230° C. When the pressure reaches atmospheric or 0 psig., the temperature is maintained at about 230° C. while sweeping with nitrogen for one hour. The reactor is slowly evacuated to about 10 mm. with a nitrogen sweep. Vacuum is then broken with nitrogen and the resin product is removed from the reactor. 
     Example 2 
     A poly(ester-amide) was prepared following the typical procedure from the following charge: 
     
         ______________________________________                              Equiva-                              lents % InMaterial        Weight   Equivalents                              Product______________________________________*Polymerized tall oil acid           626      2.2       25Adipic acid     161      2.2       25Hexamethylene Diamine           220      2.64      30(70% solution)Ethylene glycol (excess)           109      3.52      20Zinc acetate - 2H.sub.2 O           1.0Antimony oxide (Sb.sub.2 O.sub.5)           0.1Triphenyl phosphate           2.0Antifoamant     10 drops(Dow Corning Antifoam A)______________________________________*Versadyme ® 288 polymerized tall oil fatty acids havingtypical specification:Acid Value 197-201% Monomer (M)       1.5    max% Intermediate (I)       3.5    max% Dimer (D) 90.0   min% Trimer (T)       5.0    max 
    
     In the foregoing the zinc acetate, antimony oxide and triphenyl phosphite are esterification catalysts, the triphenyl phosphite also serving as an antioxidant. The resulting product contains about 37% by weight of ester segments and about 63% amide segments. On an equivalent basis the product contains 25 equivalent percent of polymerized tall oil fatty acids, 25 equivalent percent adipic acid, 30 equivalent percent hexamethylene diamine and 20 equivalent percent ethylene glycol. The product had the following properties: 
     
         ______________________________________Acid No.               32.0 meg/KgAmine No.              44.8 meg/KgOH No.                 169.0 meg/KgBall &amp; Ring            198° C.Softening PointInherent Viscosity     0.534Yield Point (psi)      845Ultimate tensile Strength (psi)                  1450% Elongation           556______________________________________ 
    
     Example 3 
     In the same manner as Example 2, a polyester-amide was prepared with the materials below to provide a product having 47% by weight ester segments and 53% amide segments. 
     
         ______________________________________                               Equiva-             Weight   Equiva-  lent % InMaterial          (grams)  lents    Product______________________________________Polymerized tall oil acid             684      2.400    30(Same as Example 2)Adipic acid       117      1.600    20Hexamethylene diamine             165      1.987    25(70% solution)Ethylene glycol   123      4.000    25Zinc acetate - 2H.sub.2 O             1.0Antimony oxide    0.1Triphenyl phosphite             2.00.1% Dow Corning Antifoam             10 drops______________________________________ 
    
     The products had the following properties: 
     
         ______________________________________Acid No.               16.1 meg/KgAmine No.              50.6 meg/KgOH No.                 174.9 meg/KgBall &amp; Ring            159° C.Softening PointInherent Viscosity     0.539Yield Point (psi)      470Ultimate tensile Strength (psi)                  730% Elongation           650______________________________________ 
    
     Examples 4-16 
     Several other polyester-amide resins were similarly prepared, the amounts and results thereof which can be seen from the following Table I. In all cases the ethylene glycol was used in a 100% excess. The equivalents of each component in the final polymer is as shown in the Table. 
     
                                           TABLE I__________________________________________________________________________      Wt. %              BrookfieldEg. in Final      Poly-       Ball &amp; Ring                         Visc. Tensile Properties     HeatPolymer    ester           Acid              Amine                  softening                         220° C.                               Tensile Strength                                           2% Modu-                                                 Elonga-                                                      FailEx.   D/A/H/E Seg. #  #   Point °C.                         (poise)                               YP (psi)                                    UTS (psi)                                           less (psi)                                                 tion                                                      °C.__________________________________________________________________________ 4 25/25/30/20      37   1.1              1.2 185    100   780  1420   14,100                                                 650  179 5 30/20/25/25      47   1.3              0.9 168    400   700  1900    9,500                                                 900  155 6 30/20/25/25*      47   3.2              0.4 194    250   610   760    8,000                                                 310  -- 7 30/20/25/25**      47   0.8              1.0 170    40    620   690   10,900                                                 410  153 8 25/25/25/25      47   0.8              1.0 179    300   750  2000   14,000                                                 865  165 9 10/40/20/30      56   0.4              0.9 185    60    1140 1300   25,000                                                 280  17210 40/10/20/30      58   0.7              1.0 127    75    430   520    5,300                                                 1065  8511 20/30/40/10      18   4.8              1.0 199    400   1320 3000   24,700                                                 460  18412 30/20/25/25      47   2.8              0.8 165    160   620  1350   10,200                                                 900  14313 30/20/25/25      47   2.2              1.1 168    75    --   1500    9,800                                                 870  15014 30/20/25/25      47   5.8              0.6 161    20    600   600   10,000                                                 450  12515 30/20/25/25      47   3.3              1.1 166    12    640   560   12,300                                                 240  12315 25/25/35/15      28   1.3              1.1 200    480   975  2700   17,000                                                 660  192Comparative A      60   7.1              0.7 196    64    510  1720   15,000                                                 455  194(Ex. 3 of U.S.P. 3,650,999)Comparative B      30   5.5              1.0 177    60    760   945    6,500                                                 385  145(Ex. 1 of U.S.P. 3,650,999)Comparative C      75   1.0              1.3 142    17    --   --     --    --   115(Ex. 3 of U.S.P. 4,343,743) - block polymer)Comparative D      75   1.0              1.0 118    35    --   --     --    --    86(Ex. 3 of U.S.P. 4,343,743 - random polymer)__________________________________________________________________________ Notes: D = Polymerized tall oil acids of Ex. 1; A = Adipic acid; H = Hexamethylene diamine; E = Ethylene glycol; *made as block copolymer  adipic acid/hexamethylene diamine block formed first **Polymerized tall oil acids  Versadyme  ® 204 having typical analysi % M 10.9; % I 5.3; % D 71.1; % T 12.6; 
    
     In the foregoing Table I, the amine and acid members are determined by conventional titration analysis. The heat fail temperature is the temperature at which a one square inch lap bond between Kraft paper fails under a three pound load using a temperature rate of 5° C./10 minutes. The other values were determined as indicated below: 
     
         ______________________________________Ball &amp; Ring Softening Point (B &amp; R)                   ASTM 28-58 TTensile Strength YP     ASTM D-1708UTS                     ASTM D-1708Modulus                 ASTM D-638Elongation              ASTM D-1708______________________________________ 
    
     In the following Table II, the adhesive properties, glass transition temperatures and flexibility of the products are shown. The adhesive properties were determined by measurement of T-peel strength determined by ASTM D-1876-72 on tin plate (TP), aluminum (AL), Mylar (M) and aluminum to Mylar (AL/M). Except where otherwise indicated the bonding temperature was 220° C. The glass transition temperatures were determined by ASTM D-4065-82 and flexibility was determined by a mandrel bend test at temperature of Room Temperature (72° F.), 0° F., and -20° F. by test method ASTM D-3111-76, with Pass (P) and Failure (F) as indicated. 
     
                                           TABLE II__________________________________________________________________________T-Peel               Flexibility - Mandrel Bend TestPounds/Inch       Tg RT    0° F.                            -20° F.ExampleTP  AL M   AL/M             °C.                1/2&#34;                  1/4&#34;                    1/8&#34;                      1/2&#34;                        1/4&#34;                          1/8&#34;                            1/2&#34;                              1/4&#34;                                1/8&#34;__________________________________________________________________________4    34  -- --  --  *  P →                    →                      →                        →                          →                            →                              →                                P5    35  9  --  --  -24                P →                    →                      →                        →                          →                            →                              →                                P6    20  4.7     5.3***         7.4 -32                P →                    →                      →                        →                          →                            →                              →                                P7    --  -- --  --  -26                P →                    →                      →                        →                          →                            →                              →                                P8*   27  6.4     5.4***         4.6 -26                P →                    →                      →                        →                          →                            →                              →                                P9    13  6.8     --  4.3 -31                P →                    →                      →                        →                          →                            →                              →                                P10** 26  4.9     8.6 7.3 -34                P →                    →                      →                        →                          →                            →                              →                                P11   13  3.9     --  4.5***             +5 P →                    →                      →                        →                          →                            →                              →                                P12   33  8  --  --  -- P →                    →                      →                        →                          →                            →                              →                                P13   41  7  5   --  -- P →                    →                      →                        →                          →                            →                              →                                P14   29  7  --  --  -- P →                    →                      →                        →                          →                            →                              →                                P15   --  -- --  --  -- P →                    →                      →                        →                          →                            →                              →                                P16   28  -- --  --  -- P →                    →                      →                        →                          →                            →                              →                                PComp. A2 2.8     4.7***         1.9 +18                P P P F →                          →                            →                              →                                FComp. B4 4.3     --  --  +14                P P P F →                          →                            →                              →                                FComp. C--  -- --  --  -42                P →                    →                      →                        →                          →                            →                              →                                PComp. D--  -- --  --  -39                P →                    →                      →                        →                          →                            →                              →                                P__________________________________________________________________________ *Bonding Temp. 200° C. **Bonding Temp. 180° C. ***Mylar Failure 
    
     Examples 17 and 18 
     In order to illustrate further the adhesive properties of the products of the invention two lots of the resin of Example 3 having 47% polyester segments were prepared and evaluated with the following results of Table III. Adhesive results with other examples are also shown. 
     
                                           TABLE III__________________________________________________________________________    Example 17          Example 18                Example 4                      Example 5                            Example 7                                  Example 12                                        Example 15                                              Example__________________________________________________________________________                                              16Heat Fail Temp.,    150   150   179   155   153   143   123   192°C.Tensile Shear, psi(ASTM D 1002)Steel    550   1005        805   825   775   665Aluminum 830   1085        1430  835   1270  715&#34;T&#34; Peel, lb/inTinplate 33    41    34                            28Aluminum  6     8Vinyl     4     5Mylar     2     1180° Peel, lb/in*(ASTM D 903)ABS      22    28          30    13    26    15Acrylic  14    20           8     2     6     5Noryl    21    31          23    13    30    15Nylon 6,6    18    27          23     6    18    15Polycarbonate    21    27          20    13    22    14XMC      19    21    32    18    11    16    14    22Aluminum 21    27          11     6    17    15Bond. Steel    21    31          34    14    29    17Galv. Steel    17    29    27    30     3    23    14    52__________________________________________________________________________ *Canvas was used as the flexible substrate 
    
     From the foregoing description and experimental data, it can be seen that the poly(ester-amide) products of the present invention exhibit unique properties including high heat resistance combined with low temperature flexibility while having good adhesion to a variety of substrates including plastic substrate, such as polyesters and polycarbonates. The products are particularly suitable for trilamination bonding of polyethylene terephthate (Mylar) and aluminum i.e. Mylar/aluminum/Mylar. Polycarbonates are in current use in automotive applications such as aerodynamic headlamps. The products of this invention are particularly useful in such automotive applications where bonding of polycarbonates to their substrates is desired.