Water-dispersible pressure-sensitive adhesive and tape made therewith
Repulpable splicing tape, especially adapted for splicing carbonless paper. The preferred adhesive is a blend of acrylate:acrylic acid copolymer, NaOH and/or LiOH KOH, and certain ethoxylated plasticizing components. A small amount of polyamide-epichlorohydrin crosslinker may also be included.
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This invention relates to water-dispersible pressure-sensitive adhesives and to normally tacky and pressure-sensitive adhesive tapes made therewith.
Papermaking and printing operations require splicing the end of one roll of paper to the beginning of another, as well as splicing together a roll after defective material is cut out. It is important that such splices be made quickly and easily, necessitating the use of an adhesive that rapidly attains maximum strength and retains it throughout subsequent operations. In an era where ecology and conservation are both vital concerns, it is important that the spliced portions not be destroyed but that they be returned to the paper mill for reprocessing; it is thus essential that the splices (particularly the adhesive which is used to make them) be water-dispersible and repulpable. This combination of requirements precludes the use of such conventional adhesives as normally tacky and pressure-sensitive rubber-resin adhesives. In the past, several water-soluble, pressure-sensitive adhesives have been devised and employed commercially, but none has been able to achieve the desired combination of physical properties and low cost.
An early adhesive used in splicing paper was polyacrylic acid, a water-soluble polymer which is rubbery in the presence of water but which becomes brittle and friable at low humidities. Sohl U.S. Pat. No. 2,838,421 discloses a splicing tape in which related rubbery polymer adhesives are blended with polypropylene glycol to impart flexibility, particularly in low humidity environments. Double-coated paper tapes made with such adhesives have been widely used in the papermaking and printing industry; although excellent in many respects, the release from the linear interleaved in the roll of tape is adversely influenced by high ambient humidity.
Peterson U.S. Pat. No. 3,441,430 discloses a splicing tape product in which the pressure-sensitive adhesive is a water-soluble acrylic acid:ether acrylate copolymer tackified with a liquid water-soluble plasticizer containing at least one ether linkage. Because of the ether linkage, this adhesive is inherently sensitive to oxidation, and its performance characteristics are greatly influenced by conditions to which it has previously been subjected. For example, exposure to high temperature (either before or after use in splicing) tends to reduce tackiness, flexibility, and repulpability. It is not always possible to protect the tape from such conditions.
Olson U.S. Pat. No. 3,661,874 discloses a water-soluble pressure-sensitive adhesive made by reacting an epoxidized rubbery polymer with a water-soluble secondary monoamine and tackifying the polymer with a water-soluble tackifier-plasticizer. When carefully formulated, this adhesive has outstanding physical characteristics, meeting all the requirements imposed by the papermaking industry, but the manufacturing process is complex and hence expensive.
Blake U.S. Pat. No. 3,865,770 discloses a water-dispersible pressure-sensitive adhesive in which an acrylate:vinyl carboxylic acid copolymer is reacted with a lower secondary or tertiary alkanolamine to impart water solubility, tackifiers (e.g., rosin) or plasticizers (oily, water-soluble polyoxyethylene compounds) being added if necessary. Adhesives of this type have excellent tackiness and heat stability, are readily repulpable, and are comparatively inexpensive. Special problems arise, however, when adhesives of this type are used to splice carbonless paper, the alkanolamine tending to volatilize and migrate, defeating the effectiveness of carbonless paper to perform its intended function, either by forming a stable complex with nickel ion which would otherwise react with a dithiooxamide derivative or by neutralizing the acidic substance which would otherwise impart color to an acid-activated dye.
Blake copending U.S. patent application Ser. No. 390,638, filed June 21, 1982 (now U.S. Pat. No. 4,413,080), discloses a water-dispersible pressure-sensitive adhesive intended for use in splicing carbonless papers. This adhesive is a blended reaction product of acrylate, acidic rosin or rosin derivative, potassium hydroxide, sodium and/or lithium hydroxide, and an oily plasticizing water-soluble polyoxyethylene compound. Although effective in many circumstances, upon exposure to elevated temperatures, the plasticizer may separate and migrate into layers of paper adjacent the splice, causing transparentization and decreased adhesion. In addition, some of the NaOH present may migrate with the plasticizer desensitizing to some extent, the color-changing ability of the carbonless paper.
SUMMARY OF THE INVENTIONThe present invention provides a water-dispersible normally tacky and pressure-sensitive adhesive having all the advantages of the adhesive of aforementioned U.S. Pat. No. 4,413,080, together with the additional advantage that it can be used to splice carbonless paper without adversely affecting its performance. Substantially no adhesive separation occurs, even in the presence of high temperatures, pressures, and humidities.
The adhesive of the invention comprises the blended reaction product of
(a) 100 parts by weight of a copolymer of monomers consisting essentially of
(1) about 60-85 weight percent of at least one monomeric acrylic acid ester of nontertiary alkyl alcohol having 4-14 carbon atoms and
(2) correspondingly about 40-15 weight percent of vinyl carboxylic acid,
(b) about 50 to 250 parts by weight of ethoxylated plasticizing components, sufficient to impart adhesion values such as to cause the adhesive to delaminate kraft paper when tested as described herein, consisting essentially of at least one of the following:
(1) up to about 125 parts by weight, but not so much as to cause adhesive separation, of one or more OH-functional ethoxylated plasticizers and
(2) one or more electrolyte-tolerant complex acidic esters of phosphoric acid and an ethoxylated nonionic surfactant, and
(c) alkaline hydroxide consisting essentially of
(1) sodium hydroxide, lithium hydroxide, or both sodium and lithium hydroxide in an amount sufficient to enhance shear strength and minimize bleeding but insufficient to cause separation of any OH-functional ethoxylated plasticizer present, not exceeding about 0.07 hydroxyl equivalent if OH-functional ethoxylated plasticizer is the only plasticizing component present, and
(2) potassium hydroxide in an amount sufficient to promote water solubility.
Preferably, tackifying rosin or rosin derivative (especially 75-150 parts by weight) is incorporated in the adhesive to promote compatibility of the ethoxylated plasticizers with the other adhesive components and to enhance adhesion to paper. Presently preferred embodiments of the invention also incorporate both OH-functional ethoxylated plasticizer and phosphoric acid ester, about 50-100 parts by weight of each proving highly satisfactory. In these embodiments, the total amount of sodium hydroxide and lithium hydroxide provides from about 0.02 to about 0.2 hydroxyl equivalent, and the potassium hydroxide provides from about 0.1 to about 0.6 hydroxyl equivalent.
Expressed in a somewhat different manner, another preferred embodiment of the invention comprises the just described adhesive wherein the blended reaction product consists essentially of
(a) 100 parts by weight of a copolymer of monomers consisting essentially of
(1) about 60-85 weight percent of at least one monomeric acrylic acid ester of nontertiary alkyl alcohol having 4-14 carbon atoms and
(2) correspondingly about 40-15 weight percent of vinyl carboxylic acid,
(b) about 100 to 250 parts by weight of plasticizing components, of which
(1) at least about 50 parts by weight are one or more acidic esters of phosphoric acid and ethoxylated alcohol or phenol derivative and
(2) the balance is made up of one or more ethoxylated diamines, and
(c) sufficient sodium hydroxide to neutralize at least about 20% of the copolymer acid function.
The phosphoric acid ester is far more electrolyte-tolerant than the OH-functional polyoxethylene plasticizers, which were described in aforementioned U.S. Pat. No. 4,413,080. As a result, these esters do not separate from the adhesive composition, even when present in large quantities, when the NaOH content is high, or when the adhesive is exposed to high temperatures, pressures, or humidities. The OH-functional ethoxylated plasticizers may still be used but must not be present in an amount sufficient to cause adhesive separation.
It is considered desirable to include an extremely small amount of polyamide-epichlorohydrin crosslinking resin; the presence of this specific crosslinking agent greatly improves both firmness and resistance to bleeding. If used in excessive amounts, however, the crosslinking resin will decrease water solubility and repulpabitity to unacceptably low levels.
As will be apparent from the ranges indicated above, substantial variations in composition are possible. To illustrate, the use of higher percentages of short-chain acrylates in a copolymer tends to increase the hardness of the adhesive, decreasing its tackiness; in such event, it is desirable to use a comparatively higher percentage of plasticizer. On the other hand, high percentages of long chain acrylates increase the tackiness of an adhesive and reduce the need for plasticizers. Similarly, the higher the percentage of vinyl carboxylic acid in the copolymer, the lower the degree of neutralization necessary to insure water-solubility. The use of such well-known acrylate monomers is iso-octyl acrylate increases the tackiness of the ultimate adhesive and improves its adhesion to paper; on the other hand, the resultant copolymer is harder to dissolve and generally requires the addition of either more rosin or more solvent than would otherwise be the case. In general, if an insufficient amount of rosin is included, ethoxylated plasticizer (if present) may tend to separate from the ionic neutralized acrylate polymer, while if too much rosin is included, the tackiness of the adhesive is reduced.
It is important to use more than one alkali metal hydroxide in connection with neutralization, the use of only sodium and/or lithium hydroxide increasing shear but tending to reduce tackiness of the adhesive to an undesirably low level. On the the other hand, neutralization with only potassium hydroxide increases the tackiness of the adhesive but decreases its shear value and increases its bleeding tendency.
Test ProceduresIt is believed that a brief explanation of certain test procedures, used to evaluate various characteristics of water-soluble pressure-sensitive adhesives and tapes made therewith, will be helpful in understanding the invention.
Rolling Ball TackIn this test an 11-mm diameter steel ball is rolled down a plane having a length of 18 cm and inclined at an angle of 21.degree.30' to a horizontal surface on which the tape to be evaluated is positioned, adhesive side up, the adhesive thickness being at least 25 micrometers. The distance the ball rolls along the horizontal adhesive surface is measured, the tack being inversely proportional to the distance. Further details of this test are found in Test Methods for Pressure Sensitive Tapes, 7th Edition, Pressure Sensitive Tape Council, Glenview, Ill. 60025, Test No. PSTC-6. Generally speaking, although not always, adhesives used in the practice of this invention will have a rolling ball tack value of no more than 15 cm. Where tape is to be used in splicing rolls of paper together at speeds of perhaps 1000 m/minute (i.e., in making so-called flying splices), tack values of less than 5 cm are greatly preferred.
Certain adhesives embodying the invention yield high rolling ball tack values (greater than 15 cm), yet adhere aggressively to paper. These adhesives, which are usually considered relatively firm, would not function well in making flying splices but would function extremely well in making finished roll splices. The following test, which is useful in evaluating the ability of both tacky and firm adhesives to adhere to paper.
180.degree. Peel Adhesion to PaperA 3.175 cm strip of kraft paper is laminated to a 5 cm.times.12.5 cm stainless steel test panel using a double-faced pressure-sensitive tape. One end of a 2.54 cm.times.25 cm strip of sample tape having a 68 g/m.sup.2 kraft paper backing is then laid over the laminated kraft paper. Uniform adhesive contact is assured by quickly (1 second) passing a 2 kg roller over the 12.5-cm sample length.
The tape is then doubled back on itself and peeled from the kraft paper surface at 30.5 cm/minute, using a method generally equivalent to that described in Test PSTC-1 "Test Methods for Pressure Sensitive Tapes", 7th Edition, Pressure Sensitive Tape Council, Glenview, Ill., 60025. If the tape adheres well to the kraft paper, the numerical result may be unimportant, as it may reflect only the force necessary to delaminate the paper surface. In such a case, delamination should be the reported result. Preferred adhesives will cause delamination.
Shear AdhesionA 2.54-cm.times.2.54-cm end portion of a 2.54-cm.times.15-cm strip of tape, formed by coating a 25-micrometer thick layer of adhesive on 68 g/m.sup.2 supercalendered kraft paper backing, is adhered to a bright annealed steel test panel and rolled down with two passes of a 2-kg roller. The panel is then clamped in a jig which is disposed at 2.degree.to the vertical, so that the 12.5-cm free end of the tape extends downward, at an angle of 178.degree. to the test panel, and a 1000-gram weight is attached to the tape end. The time for the tape to separate from the panel is reported in to the nearest minute, the shear strength being directly related to the elapsed time. Further details are found in the aforementioned Test Methods for Pressure-Sensitive Tapes, Test PSTC-7. For tapes made with adhesive of this invention, it is desirable to have shear time as high as possible, preferably exceeding 100 minutes, although an extremely tacky adhesive may be satisfactory if its shear time is as low as 40 minutes.
RepulpabilityA 20-cm.times.2.54-cm strip of double-coated splicing tape is sandwiched between two 20-cm.times.2.54-cm strips of blotter paper* and cut into approximately 1.5-cm squares. To these squares are added a sufficient number of 1.5-cm squares of blotter pater to make a total of 15 grams, after which all the squares are placed in a Waring Blendor with 500 ml of water. After the blendor has run for 20 seconds, the stock that has splattered up the sides and onto the cover is washed back into the bottom with a water bottle. The blendor is again run for 20 seconds, washed as before, and run for a final 20 seconds. The stock is then removed from the blendor, rinsed twice with water, and made into a hand sheet, using a large sheet mold. The sheet is couched off the mold, pressed between blotters for 11/2 minutes in a hydraulic press, removed, dried, and examined for any particles of unrepulped splicing tape. If no such particles are present, the tape is considered satisfactory. Further details are found in TAPPI Test UM-213.
*For tape having adhesive on only one side, two 20-cm.times.2.54-cm strips are adhered to blotter paper.
The foregoing test does not apply to tape products where, e.g., the backing is a polyester film, which does not lend itself to repulping. Such backings are strong, however, and may be used in splicing tape, provided the loosened backing is mechanically removed from the beater.
The rolling ball tack test and repulpability test are equally applicable to transfer tapes, where the adhesive layer, (or, optionally two layers of adhesive flanking a fibrous reinforcing layer) is carried by a strippable release liner. In using such tapes, the exposed surface of the adhesive is placed in contact with a first sheet of paper, the liner stripped away, and a second sheet of paper adhered to the newly exposed adhesive surface.
Plasticizer Separation and Carbonless Paper DeactivationSince carbonless papers function by the interaction of chemical materials on two separate paper surfaces, samples for this test must be prepared using both of the papers involved. A 2.54-cm strip of the subject tape is adhered to the side of the paper opposite the coated side to be evaluated and the resulting laminate placed in a 65.degree. C. oven for 24 hours, after which the paper is examined for plasticizer separation and absorption into the paper, as evidenced by transparentization. Each of the taped samples is then paired with a fresh sheet of the complementary paper. The paired sheets are placed in a typewriter and a message is typed over the area where the tape has been in contact with the paper. Any abnormality in the development of the carbonless image is noted.
Bleeding TendencyThis test qualitatively measures the tendency of an adhesive to bleed through a paper sheet when subjected to pressure and/or elevated temperatures. Strips of double-faced tape, both adhesive coatings being on the type to be evaluated, are placed between two sheets of the paper chosen, after which several additional sheets of the paper are laid on each side of the sandwich formed. The resultant sample is placed in a platen press for 15 hours at about 10 kg/cm.sup.2 pressure and 40.degree. C. and subsequently examined. Bleeding is deemed "slight" and the adhesive is considered acceptable if it bleeds no more than slightly into the first sheet and does not adhere to the second sheet. If it bleeds through the first sheet and adheres only lightly to the second (i.e., blocks), it is considered less desirable but may be acceptable. Unsatisfactory adhesives adhere tightly to, and possibly bleed through, a second sheet, a condition designated "severe". Results obtained in this test will, of course, vary with the specific paper used and the ambient humidity and temperature, but comparisons of tapes run within the same set can usually be made with validity.
DESCRIPTION OF PRESENTLY PREFERRED EMBODIMENTSIt is believed that understanding of the invention will be enhanced by considering several illustrative but non-limiting examples. In each case, an acrylate:vinyl carboxylic acid copolymer was prepared, generally as described in Ulrich U. S. Pat. No. Re. 24,906. The monomers to be copolymerized were dissolved in ethyl acetate and, using azobisisobutyronitrile as a catalyst, the solution held at 53.degree. C. for 24 hours, at which time polymerization was largely completed. To the resultant viscous solution was then added sufficient methanol to reduce the solids content to about 20-22%.
A separate composition was prepared by mixing phosphoric acid ester and/or OH-functional ethoxylated plasticizer, methanol, water, and alkali metal hydroxides. When rosin or rosin derivatives are used, they are introduced into this composition. Mixing time is increased when solid rosin is present. The final mixture is a clear, colorless to amber, low viscosity solution. Appropriate amounts of the composition were blended into the acrylate:vinyl carboxylic acid copolymer, yielding a clear, substantially colorless to amber solution. This solution was coated directly on a 68 g/m.sup.2 supercalendered kraft paper backing and the solvent evaporated to leave a layer of normally tacky and pressure-sensitive adhesive on the order of 25 micrometers thick. The resultant tape product was then evaluated, using the previously described test procedures.
For convenience, the examples are set forth below in tabular form, all prepared substantially in accordance with the procedure just described, parts and percentages being by weight unless otherwise noted. The effect of varying the types, ratios, and amounts of various components will be readily apparent from examining the reported data. In many instances, adhesives which perform unsatisfactorily are capable of ready modification to improve their performance significantly. The following abbreviations have been employed:
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Acrylate monomers
BA butyl acrylate
IOA iso-octyl acrylate
Vinyl Carboxylic Acid Monomers
AA acrylic acid
Rosins
TORD disproportionated tall oil rosin
TORP polymerized tall oil rosin
WR wood rosin
WRH hydrogenated wood rosin
WRP polymerized wood rosin
Phosphoric Acid Esters
PE-510 clear to slightly hazy, viscous
liquid having an aromatic
hydrophobic base, a density of
1.08-1.09, and an acid number (mg
KOH/g product) to first
inflection point (pH 5.5) of
49-59, available from GAF
Corporation under the registered
trademark "Gafac" PE-510
RE-610 Slightly hazy, viscous liquid
having an aromatic hydrophobic
base, a density of 1.10-1.12, and
an acid number of 62-72,
available from GAF Corporation as
"Gafac" RE-610
RS-610 Hazy, viscous liquid having an
aliphatic hydrophobic base, a
density of 1.04-1.06, and an acid
number of 75-85, available from
GAF Corporation as "Gafac"
RS-610.
OH-Functional Ethoxylated Plasticizers
T/13 PEG-3 tallow aminopropylamine,
available from Armak under the
registered trademark
"Ethoduomeen" T/13
T/20 PEG-10 tallow aminopropylamine,
available from Armak as
"Ethoduomeen" T/20
T/25 PEG-15 tallow aminopropylamine,
available from Armak as
"Ethoduomeen" T/25
("PEG" followed by a number refers to moles of
polyoxyethylene glycol.)
152 Ethoxylated octylphenol having an
oxyethylene content of about 52%,
available from GAF Corporation
under the registered trademark as
"Igepal" CA-520
162 Ethoxylated nonylphenol having an
oxyethylene content of about 63%,
available from GAF Corporation as
"Igepal" CO-630
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__________________________________________________________________________
METAL HYDROXIDE
NaOH KOH
% CO- % CO-
COPOLYMER POLYMER POLYMER
PARTS PARTS
PARTS COOH OH COOH OH COOH
EX. BA IOA AA EQUIV EQUIV FUNCTION
EQUIV FUNCTION
__________________________________________________________________________
1 75 -- 25 0.347 0.208 60 0.223 64
2 75 -- 25 0.347 0.208 60 0.223 64
3 75 -- 25 0.347 0.208 60 0.223 64
4 75 -- 25 0.347 0.208 60 0.223 64
5 75 -- 25 0.347 0.208 60 0.223 64
6 75 -- 25 0.347 0.278 80 0.223 64
7 75 -- 25 0.347 0.347 100 0.235 68
8 75 -- 25 0.347 0.174 50 0.186 54
9 75 -- 25 0.347 0.139 40 0.186 54
.[.10
75 -- 25 0.347 0.139 40 0.477 137.].
11 75 -- 25 0.347 0.139**
40** 0.464 134
12 75 -- 25 0.347 0.139 40 0.471 136
13 75 -- 25 0.347 0.139 40 0.483 139
14 75 -- 25 0.347 0.139 40 0.520 150
15 75 -- 25 0.347 0.139 40 .[.0.186.]..Iadd.0.255.Iaddend.
2 73
16 75 -- 25 0.347 0.208 60 0.198 57
17 75 -- 25 0.347 0.208 60 0.198 57
18 75 -- 25 0.347 0.035 10 0.469 135
19 75 -- 25 0.347 0.035 10 0.469 135
20 75 -- 25 0.347 0.035 10 0.469 135
21 75 -- 25 .Iadd.0.347.Iaddend..[.0.208.].
0.104 30 0.321 92
22 75 -- 25 .Iadd.0.347.Iaddend..[.0.208.].
0.104 30 0.321 92
23 75 -- 25 .Iadd.0.347.Iaddend..[.0.208.].
0.052 15 0.607 175
24 75 -- 25 .Iadd.0.347.Iaddend..[.0.208.].
0.035 10 0.296 83
25 75 -- 25 .Iadd.0.347.Iaddend..[.0.208.].
0.035 10 0.321 92
26 75 -- 25 .Iadd.0.347.Iaddend..[.0.208.].
0.035**
10** 0.246 71
27 75 -- 25 .Iadd.0.347.Iaddend..[.0.208.].
0.035 10 0.322 93
.[.28
75 -- 25 0.208 0.035 10 0.357 103.].
29 75 -- 25 .Iadd.0.347.Iaddend..[.0.208.].
0.035 10 0.383 110
.[.30
75 -- 25 0.208 0.035 10 0.383 110.].
.[.31
75 -- 25 0.208 0.035 10 0.401 116.].
.[.32
75 -- 25 0.208 0.035 10 0.248 71.].
33 75 -- 25 .Iadd.0.347.Iaddend..[.0.208.].
0.017 5 0.376 108
34 75 -- 25 .Iadd.0.347.Iaddend..[.0.208.].
0.017 5 0.401 116
.[.35
75 -- 25 0.208 -- -- -- --.].
36 75 -- 25 0.347 0.069 20 0.186 54
37 75 -- 25 0.347 -- -- 0.394 114
38 75 -- 25 0.347 0.208 60 0.149 43
.[.39
75 -- 25 0.347 0.208 60 0.149 43.].
40 75 -- 25 0.347 0.208 60 0.074 21
.[.41
75 -- 25 0.347 0.208 60 0.074 21.].
42 75 -- 25 0.347 0.208 60 -- --
.[.43
75 -- 25 0.347 0.208 60 -- --.].
44 75 -- 25 0.347 0.208 60 0.273 79
45 75 -- 25 0.347 0.208 60 0.322 93
46 75 -- 25 0.347 0.416 120 -- --
47 75 -- 25 0.347 0.364 105 -- --
48 75 -- 25 0.347 0.139 40 0.124 36
.[.49
75 -- 25 0.347 0.139 40 0.124 36.].
50 75 -- 25 0.347 0.139 40 0.099 29
51 75 -- 25 0.347 0.139 40 0.074 21
52 75 -- 25 0.347 0.139 40 0.052 15
53 75 -- 25 0.347 0.139 40 0.124 36
54 75 -- 25 0.347 0.139 40 0.124 36
55 75 -- 25 0.347 0.139 40 0.124 36
56 75 -- 25 0.347 0.139 40 0.124 36
57 75 -- 25 0.347 0.139 40 0.124 36
58 75 -- 25 0.347 0.139 40 0.124 36
59 75 -- 25 0.347 0.139 40 0.124 36
60 75 -- 25 0.347 0.139 40 0.124 36
61 75 -- 25 0.347 0.174 50 0.198 57
62 75 -- 25 0.347 0.174 50 0.198 57
63 75 -- 25 0.347 0.174 50 0.198 57
64 75 -- 25 0.347 0.139 40 0.198 57
65 75 -- 25 0.347 0.139 40 .Iadd.0.396.Iaddend..[.0.296.].
114
66 75 -- 25 0.347 0.139 40 0.434 125
67 75 -- 25 0.347 0.208 60 0.356 103
68 75 -- 25 0.347 0.208 60 0.489 141
69 75 -- 25 0.347 0.208 60 0.623 179
70 85 -- 15 0.208 0.208 100 0.174 84
71 80 -- 20 0.278 0.208 75 0.174 63
72 80 -- 20 0.278 0.208 75 0.198 71
73 70 -- 30 0.416 0.208 50 0.223 54
74 65 -- 35 0.486 0.208 43 0.23 46
75 60 -- 40 0.555 0.208 39 0.223 40
76 45 30 25 0.347 0.208 60 0.223 64
77 64 16 20 0.278 0.028 75 0.174 .Iadd.63.Iaddend..[.64.
].
78 64 16 20 0.278 0.028 75 0.198 78
.[.79
64 16 20 0.278 0.174 62 0.421 151.].
80 64 16 20 0.278 0.174 62 0.421 151
81 64 16 20 0.278 0.174 62 0.446 .Iadd.160.Iaddend..[.12
6.].
82 64 16 20 0.278 0.174 62 0.421 151
83 64 16 20 0.278 0.174 63 0.198 71
__________________________________________________________________________
%
POLY-
PLASTICIZERS AMIDE:
OH- EPI- ROLL-
FUNCTIONAL
ROSIN CHLORO
ING SHEAR
BLEED-
ETHOXY- OR ROSIN HYDRIN
BALL ADHE-
ING
H.sub.3 PO.sub.4
ESTER
LATED DERIVATIVE CROSS-
TACK,
SION,
TEN-
TYPE PARTS
TYPE
PARTS
TYPE PARTS
LINKER
CM MIN. DENCY
__________________________________________________________________________
1 PE-510
231 -- -- -- -- -- .[.2.9.].
38 NONE
2 PE-510
231 -- -- -- -- 0.031 1.9 67 NONE
3 PE-510
231 -- -- -- -- 0.062 1.9 117 NONE
4 PE-510
231 -- -- -- -- 0.093 2.2 205 NONE
5 PE-510
231 -- -- -- -- 0.125 1.9 215 NONE
6 PE-510
238 -- -- -- -- 0.125 2.5 65 NONE
7 PE-510
243 -- -- -- -- -- 1.6 88 NONE
8 PE-510
191 -- -- -- -- -- 2.5 48 NONE
9 PE-510
191 -- -- -- -- -- 2.9 38 SL
.[.10
PE-510
80 T/20
-- WRH 136 -- 5.5 186 --.].
11 PE-510
75 163 79 WRH 136 -- 17.0 296 --
12 PE-510
75 163 79 WRH 136 -- 10.4 211 --
13 PE-510
80 163 74 WRH 136 -- 4.1 320 --
14 PE-510
126 163 53 WRH 136 -- 5.6 111 --
15 PE-510
191 -- -- -- -- -- 2.5 48 NONE
16 PE-510
203 -- -- -- -- -- 3.2 60 NONE
17 PE-510
203 -- -- -- -- 0.125 2.9 290 NONE
18 PE-510
95 163 75 WRH 86 0.375 2.8 1270 --
19 PE-510
95 163 75 WRH 86 0.50 2.2 1136 --
20 PE-510
95 163 75 WRH 86 0.625 3.7 965 --
21 PE-510
71 163 50 WRH 86 -- .[.2.0.].
.[.517.].
--
22 PE-510
71 163 75 WRH 86 -- 9.6 230 --
23 PE-510
172 T/20
50 WRH 92 0.125 2.1 70 --
24 PE-510
47 163 75 WRH 86 -- .[.65+.].
.[.519+.].
--
25 PE-510
71 163 50 WRH 86 -- 15+ .[.584+.].
--
26 -- -- 163 125 WRH 86 -- 12.0 338 --
27 PE-510
71 163 75 WRH 86 -- 8.5 177 --
.[.28
PE-510
48 163 75 WRH 86 -- 8.3 1417 --.].
29 PE-510
71 163 50 WRH 86 0.094 10.0 1036 --
.[.30
PE-510
71 163 75 WRH 86 0.094 4.7 890 --.].
.[.31
PE-510
95 163 75 WRH 86 0.125 3.3 625 --.].
.[.32
-- -- 163 125 WRH 86 0.156 8.1 799 --.].
33 PE-510
48 163 75 WRH 86 -- 10.8 340 --
34 PE-510
71 163 50 WRH 86 -- 16.7 329 --
.[.35
PE-510
80 T/25
74 -- -- -- 8.3 250 --.].
36 PE-510
191 -- -- -- -- -- 6.0 23 MOD.
37 PE-510
191 -- -- -- -- -- .[.2.9.].
34 SEV.
38 PE-510
231 -- -- -- -- -- 1.9 24 --
.[.39
PE-510
231 -- -- -- -- -- 2.2 237 --.].
40 PE-510
231 -- -- -- -- -- 1.6 18 --
.[.41
PE-510
231 -- -- -- -- -- 1.9 197 --.].
42 PE-510
231 -- -- -- -- -- 1.3 11 --
.[.43
PE-510
231 -- -- -- -- -- 1.9 40 --.].
44 RE-610
228 -- -- -- -- -- 3.2 16 --
45 RS-610
226 -- -- -- -- -- 4.8 17 --
46 PE-510
235 -- -- -- -- -- 4.4 75 --
47 PE-510
235 -- -- -- -- -- 3.8 26 --
48 PE-510
125 T/20
83 WRH 75 -- .[.2.5.].
.[.36.].
--
.[.49
PE-510
125 T/20
83 WRH 75 -- 3.5 165 --.].
50 PE-510
100 T/20
83 WRH 75 -- 2.9 77 --
51 PE-510
75 T/20
83 WRH 75 -- 3.2 307 --
52 PE-510
50 T/20
83 WRH 75 -- 10.2 1562 --
53 PE-510
125 T/25
83 WRH 75 -- 2.2 67 --
54 PE-510
125 T/20
55 WRH 50 -- 3.8 75 --
55 PE-510
125 T/20
28 WRH 25 -- 5.1 63 --
56 PE-510
125 T/20
83 TORP 75 -- 4.8 100 --
57 PE-510
125 T/20
83 WRP 75 -- 4.8 81 --
58 PE-510
125 T/20
83 TORD 75 -- 2.2 64 --
59 PE-510
125 T/20
83 WR 75 -- 3.8 63 --
60 PE-510
126 T/13
83 .Iadd.WRH.Iaddend..[.WRD.].
75 -- 3.8 86 --
61 PE-510
203 T/20
27 WRH 13 -- 3.8 36 --
62 PE-510
203 T/20
27 -- -- -- .[.1.9.].
29 --
63 PE-510
203 T/20
54 -- -- -- 1.6 24 --
64 RE-610
211 -- -- WRH 68 -- 4.1 29 --
65 PE-510
200 -- -- WRH 68 -- 3.2 .[.29.].
--
66 RE-610
198 -- -- WRH 68 -- 3.2 34 --
67 PE-510
179 -- -- WRH 47 -- 7.9 114 --
68 PE-510
179 -- -- WRH 94 -- 3.0 .[.100.].
--
69 PE-510
179 -- -- WRH 140 -- 2.5 125 --
70 PE-510
180 -- -- -- -- -- 7.0 19 --
71 PE-510
180 -- -- -- -- -- 3.2 39 --
72 PE-510
205 -- -- -- -- -- 1.6 10 --
73 PE-510
231 -- -- -- -- -- 3.2 49 --
74 PE-510
231 -- -- -- -- -- 5.1 42 --
75 PE-510
231 -- -- -- -- -- 8.6 61 --
76 PE-510
231 -- -- -- -- -- 3.2 16 --
77 PE-510
180 -- -- -- -- -- 2.9 31 --
78 PE-510
205 -- -- -- -- -- 1.3 31 --
.[.79
PE-510
25 163 74 WRH 138 -- 6.8 178 --.].
80 PE-510
26 163 107 WRH 138 -- 3.1 112 --
81 PE-510
51 163 107 WRH 138 -- 2.7 54 --
82 PE-510
26 152 134 WRH 138 -- 3.1 .[.164.].
--
83 PE-510
203 T/20
27 -- -- -- 1.3 34 --
__________________________________________________________________________
*based on total adhesive solids
**LiOH used instead of NaOH
Those persons skilled in the art will recognize that it is not feasible to set forth all the variations to which this invention is susceptible, and many modifications will readily suggest themselves, especially if certain principles are borne in mind. For example, the shorter the chain length of the alcohol from which the acrylate monomer is derived, the firmer the resultant pressure-sensitive adhesive. If a softer adhesive is desired, the chain length of the alcohol may be increased. If greater shear strength for an adhesive made with a given copolymer is desired, a higher molecular weight, as evidenced by a higher inherent viscosity, can be used; alternatively, a small amount of a crosslinking agent can be incorporated if repulpability is not compromised in the final adhesive.
Other monomers such as fumarates may be incorporated to provide side chain attachments to the polymer backbone through pendent ester linkages in the same manner as acrylate esters.
It will likewise be recognized that, to achieve specific results, it may be desirable to incorporate minor amounts of monomeric modifiers into copolymers used to formulate adhesives of the invention, for example, styrene or methyl methacrylate increases firmness, tertiary butyl styrene increases tack, etc. Similarly, dyes, pigments, fillers, etc. may be added where necessary or desirable.
Although this information has been particularly described with respect to a splicing tape for papermaking and printing operations, the pressure-sensitive adhesive has many other uses. For example, water-soluble adhesive labels may be applied to dishes, windows, or other surfaces which it is commmon to clean with aqueous solvent. Cloth labels coated with this adhesive may readily be washed from garments to which they are affixed. Likewise, since the adhesive is substantially insoluble in most oils or similar hydrocarbon solvents, it may be employed in applications where conventional normally tacky and pressure-sensitive adhesive tapes prove unsatisfactory.
Claims
1. Normally tacky and pressure-sensitive water-dispersible adhesive especially suitable for splicing carbonless paper, comprising the blended reaction product of
- (a) 100 parts by weight of a copolymer of monomers consisting essentially of
- (1) about 60-85 weight percent of at least one monomeric acrylic acid ester of nontertiary alkyl alcohol having 4-14 carbon atoms, and, correspondingly,
- (2) about 40-15 weight percent of vinyl carboxylic acid,
- (b) about 50 to 250 parts by weight of ethoxylated plasticizing components, sufficient to impart adhesion values such as to cause the adhesive to delaminate kraft paper when tested as described herein, consisting essentially of at least one of the following:
- (1) up to about 125 parts by weight, but not so much as to cause adhesive separation, of one or more OH-functional ethoxylated plasticizers and
- (2) one or more electrolyte-tolerant complex acidic esters of phosphoric acid and an ethoxylated nonionic surfactant, and
- (c) alkaline hydroxide consisting essentially of
- (1) sodium hydroxide, lithium hydroxide, or both sodium hydroxide and lithium hydroxide, in an amount sufficient to enhance shear strength and minimize bleeding but insufficient to cause separation of any OH-functional ethoxylated plasticizer present, not exceeding about 0.07 hydroxyl equivalent if OH-functional ethoxylated plasticizer is the only plasticizing component present, and
- (2) potassium hydroxide in an amount sufficient to promote water solubility.
2. The adhesive of claim 1 wherein the total amount of sodium hydroxide and lithium hydroxide provides from about 0.02 to about 0.2 hydroxyl equivalent and the potassium hydroxide provides from about 0.1 to about 0.6 hydroxyl equivalent.
3. The adhesive of claim 1 wherein the blended reaction product consists essentially of
- (a) 100 parts by weight of a copolymer of monomers consisting essentially of
- (1) about 60-85 weight percent of at least one monomeric acrylic acid ester of nontertiary alkyl alcohol having 4-14 carbon atoms, and, correspondingly,
- (2) about 40-15 weight percent of vinyl carboxylic acid,
- (b) about 100 to 250 parts by weight of plasticizing components, of which
- (1) at least about 50 parts by weight are one or more acidic esters of phosphoric acid and ethoxylated alcohol or phenol derivative and
- (2) any balance is made up of one or more ethoxylated diamines or ethoxylated phenols, and
- (c) sufficient sodium hydroxide to neutralize at least about 5% of the copolymer acid function.
4. The adhesive of claim 3 wherein the acrylic acid ester comprises butyl acrylate and the vinyl carboxylic acid comprises acrylic acid.
5. Normally tacky and pressure-senstive adhesive tape comprising a layer of the adhesive of claim 3 coated on a sheet backing.
6. The tape of claim 5 wherein a tackifying rosin or rosin derivative is included in the adhesive.
7. The tape of claim 5 wherein an extremely small amount of polyamide-epichlorohydrin crosslinking resin is included in the adhesive.
8. The tape of claim 5 wherein the adhesive consists essentially of 100 parts of a butyl acrylate: acrylic acid copolymer having a COOH equivalent in the approximate range of 0.25 to 0.45, sufficient NaOH to provide approximately 0.02-0.2 OH equivalent, sufficient KOH to provide approximately 0.1-0.6 OH equivalent, about 50-250 parts of plasticizer, and 0.08-0.50% by weight polyamide-epichlorohydrin resin crosslinker based on total adhesive solids.
9. The adhesive of claim 1 wherein the plasticizing components include both OH-functional ethoxylated plasticizer and acidic ester of phosphoric acid and ethoxylated alcohol or phenol derivative.
10. The adhesive of claim 9 wherein about 50 to 100 parts by weight of oily ethoxylated plasticizer are present.
11. The adhesive of claim 10 wherein about 50 to 100 parts by weight of the phosphoric acid ester are present.
12. The adhesive of claim 11 wherein from about 75 to about 150 parts by weight of rosin or rosin derivative are present.
13. Normally tacky and pressure-sensitive adhesive tape comprising a layer of the adhesive of claim 12 coated on a sheet backing.
14. The tape of claim 13 wherein an extremely small amount of polyamide-epichlorohydrin resin crosslinker is included in the adhesive.
| 2838421 | June 1958 | Sohl |
| 3441430 | April 1909 | Peterson |
| 3661874 | May 1972 | Olson |
| 3865770 | February 1975 | Blake |
| 4322516 | March 30, 1982 | Wiest et al. |
| 4337284 | June 29, 1982 | Cooper et al. |
| 4341680 | July 27, 1982 | Hauber et al. |
| 4413080 | November 1, 1983 | Blake |
| 4413082 | November 1, 1983 | Gleichenhagen et al. |
| 2904233A1 | August 1980 | DEX |
| 3105894C2 | December 1982 | DEX |
Type: Grant
Filed: Apr 27, 1992
Date of Patent: Jun 8, 1993
Assignee: Minnesota Mining and Manufacturing Company (St. Paul, MN)
Inventor: Frederick D. Blake (Woodbury, MN)
Primary Examiner: Edith Buffalow
Attorneys: Gary L. Griswold, Walter N. Kirn, John H. Hornickel
Application Number: 7/878,289
International Classification: C08K 332;
