Block copolymer adhesive compositions and articles prepared therefrom

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PATENTS AND REGISTRATION OFFICE

PUBLISHING WRITING No. 326 294 ln, Cl c 08 d 9/02 Kl. 39 b? 9/02

C 08 f 41/10 39 b^{* 4} 41/10

Patent Application. No. 7686/64 Received on 24 VI 1964 Validity Date on 24 VI 1964 Ans. generally available on 1 VII 1968

Ans. laid out and the pamphlet published 20 VII 1970

Priority requested from 26 VI 1963 (United States, 290,710)

SHELL INTERNATIONALE RESEARCH MIJ NV, HAAG, NETHERLANDS Inventor: JT Harlan jr Agents: E Lindquist Binder mixture

The invention relates to binder mixtures with improved tackiness and cohesion strength.

There are numerous binder mixtures based on natural and synthetic materials of various kinds. At present, an increasing number of binders containing synthetic high polymers are produced in admixture with resins, which increase the tackiness.

fillers, plasticizers, stabilizers, extenders, etc. For the most part, however, these binders are subject to certain technical or economic constraints.

In all cases, the properties (strength, stability, tackiness, etc.) must be balanced against the total bonding costs.

One of the problems in producing binder mixtures is not so much related to the ability of the binder to adhere to a material, for example paper, metal, plastic etc., as to the internal cohesive strength of the binder. Materials that are known to confer high cohesive strength have deficiencies. The use of cross-linked polymers, for example cured epoxy resins or cured gums, necessitates special treatment, which often makes materials of this type undesirable. On the other hand, non-crosslinked polymers usually have low strength at temperatures below their glass transition point and are hard and brittle at temperatures above that point. Some materials exhibit higher cohesion strength in combination with flexibility, such as neoprene and polyamides, but the cost of these materials is inappropriately high compared to the cost of conventional binder components.

Petroleum oils and the like have been included in the binders to increase flexibility and reduce the cost of binder mixtures containing polymers, e.g.

Dupl.kl. 8 1: 4 $ 22 i: 1 $ 22 i: 2; 39 b⁴: $ 25.00 $ 39 b⁴: 35/06 $ 55 f: 16

ITY

326294 ₂ natural rubber, but this must be strictly limited due to the rapid deterioration of the cohesive strength of the mixture which such oils cause. However, such oils are so inexpensive that their use would be particularly attractive if one could obtain a composition in which they could be included with substantial levels without degrading the properties of the resulting mixtures.

The synthetic rubber, the tackiness of the resin and a lubricating oil containing the binder mixture of the invention are characterized in that the synthetic rubber is an uncured segment copolymer of the general formula

A - B - A where A is a polystyrene or poly-2-vinyl-pyridine segment with a calculated molecular weight in the range 10,000 - 100,000 and B is a polybutadiene or polyisoprene segment with a calculated molecular weight in the range 25,000 - 150 000, wherein segment A is 20-80% by weight of the copolymer and has a glass transition point above 50 ° C, and the segment denoted by B has a glass transition point that differs at least 100 degrees centigrade from the glass transition point of segment A, and the mixture, based on 100 parts by weight of said segment copolymer, contains 25-300 parts by weight of the tackifying resin and 25-135 parts by weight of a petroleum exfoliating oil having an aromatic content of less than 30% by weight, a viscosity in the range 2-20 cP at 99 ° 0 and an initial boiling point exceeding 288 ° C.

One of the most important criteria for segment polymerisates suitable for the binder mixtures of the invention is that one segment should be non-elastic and the other elastic. By elastic, it is meant that the polymer meets the requirements set out in ASTM special technical bulletin no. 184, Philadelphia, USA, 1959, namely: A material which at room temperature can be stretched to at least twice its original length and after the elongation and after the elongation force is eliminated, with force and in a short time is re-aggregated to a length approximately equal to with its original length. Thereby, the elastic polymer segment differs from the non-elastic ones.

Figures 1 and 2 illustrate the relationship between composition and two important properties of contact adhesive adhesives, namely cohesion strength and tackiness. Figure 1 shows the dependency of the stickiness on the resin: oil ratio and Figure 2 shows the cohesion strength dependence on the resin: oil ratio. In both figures, the abscissa shows the amount of oil in parts by weight per 100 parts by weight of segment polymerized and on the ordinate the resin amount in parts by weight per 100 parts by weight of segment polymerisate. In Figure 1, the figures assigned to the curves refer to stickiness (Hercules Thank You - see The Hercules Drop Method for Determining the Softening Point of Rosins and Modified Rosins, No. Herc. 400-431 C, 1955) in grams for a diameter 1 probe. , 6 mm. In Figure 2, the figures assigned to the curves refer to the shear cohesion strength in kp for an overlap joint 2.54 x 2.54 cm. In Figure 2, maximum cohesion strength is obtained at about 75 ° C (parts by weight per 100 parts by weight of segment polymerized) oil and 100% resin. However, a large area falls within the curve of 45.4 kp and this cohesive strength is more than sufficient for all common applications for adhesive adhesive. It can be seen from Figure 1 that stapling exceeding 1250-1500 g (comparable to the staple obtained with natural rubber control samples and commercially available, contact adhesive cellophane tape) can be obtained in an elongated range from about 20% by weight of oil and 50% by weight to $ 6. resin to about 100 wt% oil and l80 wt / resin.

The tackiness of the adhesive adhesive or its ability to adhere to a surface is composed of a number of other properties, for example surface tack, tensile strength, viscosity, hardness, etc. When it is a time and pressure dependent property, tackiness must be measured under specific conditions. In the present context, the following conditions have been selected: 1 second and a pressure of 10 grams with a contact surface of brass with a diameter of 1.6 mm. This property is measured according to the method described by Wetzel in The Characterization of Pressure Sensitive AdI hesives, ASTM Bulletin No. 221, pp. TP 72-? 6, April 195 ?.

In modern fast manufacturing, such as shoes and cardboard boxes, there is an ever-growing need for strong binders that, when applied in molten form, develop strength and lose tack in a few seconds. These high temperature melting adhesives are relatively new products and the need for them grows rapidly as more efficient, continuously operating applicators are constructed. Previously, low molecular weight waxes and resins have been used, but these have low strength, unsuitable rigidity and cure relatively slowly.

More useful binders are produced by mixing high molecular weight polymers, such as polyvinyl acetate, but elastomers such as natural rubber have not found general use. Newer materials, such as polyamides, are used, but these materials condition high prices. The compositions of the invention are not only inexpensive but can be formulated to meet physical requirements for high temperature melting adhesives which fall within the scope of the invention. The blends have been found to be excellent for bonding polar substances such as leather, polyvinyl chloride, paper, etc.

Elastatex binders find use especially for gluing leather, fabric, plastic, paper, etc., for example in the manufacture of shoes and packaging materials. Previously, non-cured natural rubber, styrene-butadiene rubber, etc. has been used when high cohesion strength is not required. When stronger joints are needed, neoprene and other expensive latexes have been used or you have to resort to mixtures of the weaker elastomers, which after use must be cured and therefore more difficult to use. Latex binders made from the compositions of the present invention can compete with neoprene latex for tackiness and cohesion strength, but they have the considerable advantage of lower material costs because it is possible to use substantial amounts of low-cost oils therein and because no subsequent curing is required.

Stable latexes can be successfully prepared from oil-extruded segment polymerisates. Thus, for example, cyclohexane solutions of the segment polymerate can be emulsified with an aqueous soap solution which can be treated to remove the solvent (cyclohexane) to obtain a latex. Iiartsct

326294 . may be mixed with the oil-extruded segment polymerate by mixing the latex with a resin emulsion or by incorporating the resin into the original solution prior to emulsification. Maximum strength of joints made with binder latex of this type is improved by heating the finished joints to temperatures of the order of 100-175 ° θ for a fraction of 1 second up to 15 minutes.

The primary component of the binder mixtures of the invention, i. segment polymerized by the general formula

A - B - A can, if desired, be fully or partially hydrated. It has the special property of exhibiting the physical properties which are characteristic of a rubber which has been cured, although the segment polymerate is not subjected to any curing treatment. for cured gums while having solubility characteristics as non-cured materials.

It is a well-known fact that most, although not all vulcanized gums with normal properties, such as natural rubber, polybutadiene, etc. become highly insoluble after being vulcanized. In addition, because they do not need to be cured, these binder mixtures are easier to use than binders made from ordinary rubber-like materials.

The segment polymerizers can be prepared using lithium-based initiators, for example, metallic lithium or lithium organic compounds either in polar or non-polar solvents. For some purposes, a high cis structure in the middle segment is suitable. This is achieved by polymerization in the presence of non-polar solvents. If a more branched structure is desired, more or less polar solvents, e.g., tetrahydrofuran and the like If the three polymer segments are prepared in a two-step process, dilitium initiators can be used or coupling reactions can be applied.

The segment polymerizers which constitute an essential component of the composition of the invention can, if desired, be modified by partial or complete hydrogenation. Selected conditions can be applied, for example, for hydration of the elastic middle segment without modifying the vinyl pyridine polymer segments. In this way.

It is also possible to choose such conditions that the hydrogenation occurs substantially uniformly along the polymer chain both in the elastic mid segment and in the non-elastic segments to substantially the same extent, and this hydration can be either partial or complete. Through the hydration can segment; the compatibility of the polymerization with the extender oils is changed, so that more and more oil types can be called into question for these mixtures.

The mixtures can, if desired, be modified with materials such as antioxidants and stabilizers. These include stabilizers for protection of both the dementite segments and the non-elastic outer segments. Combinations of stabilizers are often more effective because segments of these types are decomposed according to different mechanisms. Some sterically hindered phenols, motal organic compounds, aromatic amines and sulfur compounds are useful for this purpose. Particularly effective materials belong to the following types:

1) benzothiazoles, such as 2- (dialkyl hydroxybenzylthio) benzothiazoles;

2) esters of hydroxybenzyl alcohols, such as benzoates, phthalates, stearates, adipates and acrylates of 3β-dialkyl-4-hydroxybenzyl alcohols;

3) tin (II) phenyl catecholates;

4) zinc dialkyl dithiocarbamates;

5) alkylphenols, for example 2,6-ditert.butyl-4-methylphenol.

Although the segment polymerates contain the major and sometimes the only elastic component of these binder mixtures, the mixtures may also contain minor amounts of other common elastomers, such as natural rubber, synthetic rubbers such as polyisoprene, polybutadiene, neoprene, polybutylene and ethylene propylene rubber.

The resins used with the segment polymerizers and oils to increase the tackiness of the binder mixture can be represented by the following sequence:

rosin, dehydrogenated rosin, rosin + polyterpene resins, for example polymerized beta-pinene (100 $ rosin to 100 $ resin) glycerol esters of hydrogenated rosin pentaerythritol esters of hydrogenated rosin coumarone-indene resins hydrogenated rosin glycerol esters of polyraeriserat rosin maleic anhydride modified rosin and rosin derivatives partial esters of styrene-maleic acid copolymers biphenyls ( SP 45 -16 ° C) oil-soluble phenol-aldehyde resins.

The main advantage of the extender oils used in conjunction with the increasing resin and segment polymerisates is that the cost of the blend is substantially reduced while the tack and flexibility are improved without any significant deterioration of the other properties of the binder blend. The oils must be carefully selected so that they are coordinated with the segment polymerisers for compatibility with the various segments. As noted above, the oil should be substantially compatible with the homopolymers forming the middle segment but substantially incompatible with homopolymers of the non-elastic (thermoplastic) outer segments. Compatibility can be determined by experiments of the following type:

326294 t _____ -. An oil to be investigated is mixed in several proportions, for example 5, 50, 1θθ w / w, with a segment polymerizer of the type of interest in a common volatile solvent, for example toluene. A thin film is cast by uniformly smoothing the solution onto a glass surface, after which the solvent (toluene) is allowed to evaporate for 16-24 hours at room temperature. The suitability of the oil as a diluent is judged by the tensile strength of the oily polymer films, which are determined in kp / cm by means of a suitable test apparatus and by the appearance of the film surface. Excessive compatibility with the outer polymeric segments results in a significant loss of tensile strength, which loss is greater than that obtained by simple dilution of the polymer. Too much inconsistency can be seen from the oil diffusing out onto the surface of the film.

Table 1 lists the properties of typical extender oils suitable for the purpose of the invention.

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From the values ​​given in the above table, it can be seen that these petroleum oils are, at relatively high temperatures, boiling materials containing only minor amounts of aromatic hydrocarbons, preferably less than about 30 and, in particular, less than about 15, although with some of the high polymer segment polymers. vinyl aromatic hydrocarbons, higher aroma extraction oils can be tolerated. In preferred embodiments of the invention, the extender oils are petroleum extender oils having aromatic content less than 30 wt / and viscosity between 2 and 20 cP at 99 ° θ and initial boiling point above 55O ° C, aromatic content preferably less than 15 wt /, viscosity between 4 and 15 cP at 99 ° C also. original boiling point above 302 ° C.

The compositions of the invention can be adapted for a wide variety of applications. They can be applied to paper, cardboard, wood, metal foil, polyolefin film, polyvinyl chloride film, cellophane, felt, woven and non-woven textiles, glass etc. and for bonding two or more such materials. The adhesive mixtures are useful as adhesives, for example for adhesive adhesive strips, masking strips, adhesive sheets, adhesive strips, repair strips, electrical insulating tapes, further as a basis for other adhesives, as adhesives in laminates, such as high temperature melting adhesive mixtures, cement, mastics, bees demedel, sealants, other types of pressure sensitive adhesives, adhesive sustained stapling, klisterlatexär, adhesive shoe soles, bottom coating for tissues, carpets, cement etc.

The following examples illustrate the use of the binder mixtures of the invention.

Example 1

Contact adhesive.

A sample of polystyrene-polyisoprene-polystyrene segment polymerized in toluene solution is mixed with a non-aromatic diluent oil and a resin which increases the tackiness. The adhesive adhesive film used for adhesive wetting is prepared by evaporation overnight at room temperature of a thin layer of this solution on a glass surface. The cohesive strength is determined by allowing several successive layers of the solution to evaporate onto two 2.54 cm wide canvas strips, after which the strips are compressed with overlap 2.54 x 2.5^J₉ · 326294 cm .. The dressing is then allowed to dry overnight and its strength is determined in an Instron tester by subjecting it 'to shear to fracture at a' tensile rate of 5 per ηιί, η.

The segment polymerate had the composition:

Polystyrene polystyrene poiyicöpren

The first polystyrene segment: Molecular weight 43,000

Polyisoprene segment: 108,000 • The last polystyrene segment: 57,000.

Weight &amp; styrene in the polymer 48

The oil had the properties listed in Table 1 under A. Hercules Powder Co. was used as a resin Poly Pale Ester-10, a polymerized rosin glycerol ester, which has a softening point determined by Hercules Drop Method amounting to 110 ° C.

The binder mixture and the results obtained are as follows

By comparison, a control sample based on natural rubber (rolled, smoked leaf rubber) is shown:

Segment The composition of the solution, parts by weight of polymeric binder

Segment polymerized 100

Natural rubber 0

Oil 75

Resin 125

Toluene \ 1200

Stabilizer^x 1

Test Results

Adhesion in grams obtained with a probe with a diameter of 1.6 mm 1950

Cohesion hold phase the t, shear force in kp for an overlap joint

2.54 x 2.54 cm 56.7

Natural rubber, control sample

100

150

1000

1400

1,4

x) Half of antioxidant 2246, a sterically hindered phenol made by American Cyanamid Co. and half Thermolite 31, a sulfur-containing, tin-organic compound made by Metal and Thermit Co.

Other examples of contact adhesive adhesives with the same components as above:

<td>The composition of the solution, parts by weight</td><td>A</td><td>B</td><td>C</td>

<td>Block copolymers</td><td> 100</td><td> 100</td><td> 100</td>

<td>Oil</td><td> 26</td><td> 135</td><td> 135</td>

<td>Resin</td><td> 158</td><td> 168</td><td> 248</td>

<td>toluene</td><td> 1200</td><td> 1200</td><td> 2000</td>

<td>Stabilizer</td><td> 1</td><td></td><td></td>

<td>Test Results</td><td></td><td></td><td></td>

<td>Adhesion in grams obtained with</td><td></td><td></td><td></td>

<td>θη probe with a diameter of 1.6 mm</td><td> 50</td><td> 135</td><td> 1300</td>

<td>Cohesion strength, shear strength ft</td><td></td><td></td><td></td>

<td>in kp for an overlap joint</td><td></td><td></td><td></td>

<td>2.54 x 2.5 cm</td><td> 54</td><td> 42</td><td> 32</td>

326294 ₁₀

All of these and other similar mixtures were used in the experiments which are the basis of the diagrams in Figures 1 and 2.

Example II High temperature melting agents.

These binder mixtures were prepared either by mixing segment polymeric, oil and resin in toluene solution and eliminating the solvent by evaporation or by mixing the components at 150 ° C.

The segment polymerizers were either polystyrene-polyisoprene-polystyrene or polystyrene-polybutadiene-polystyrene segment polymeric, which as oil was used under A in Table 1. As a resin, a coumarone indene resin with softening point 94-107 ° C (ball and ring with shoulder) was used.

<td>The composition of the solution</td><td>A</td><td>B</td>

<td>Elastic center segment</td><td>polybutadiene</td><td>polyisoprene</td>

<td>First polystyrene segment,</td><td></td><td rowspan="2"> 87.000</td>

<td>molecular weight</td><td> 22.000</td>

<td>Middle segment, molecular weight The last polystyrene segment,</td><td> 62.000</td><td> 17.000</td>

<td>molecular weight</td><td> 20.000</td><td> 55.000</td>

<td>Weight / styrene in the polymer</td><td> 41</td><td> 89</td>

<td>Binder mixture (toluene</td><td></td><td></td>

<td colspan="3">free) parts by weight</td>

<td>Block copolymers</td><td> 100</td><td> 100</td>

<td>Oil</td><td> 100</td><td> 100</td>

<td>Resin</td><td> 100</td><td> 100</td>

<td>Stabilizer (same as in Example I) Test Results</td><td> 1</td><td> 1</td>

<td colspan="3">Cohesion strength, shear force in kp for an overlap joint</td>

<td>2.54 x 2.54 cm</td><td> 69,4</td><td> 14</td>

Sample B, whose polystyrene resin is outside the limits required by the invention, shows that too low cohesion strength is obtained if the non-elastic outer segments make up too much of the segment polymerate.

Example III Latex Stickers

Latex adhesives were prepared by mixing together a latex of segment polymer and oil and a water resin of a resin. The oil-extruded segment polymer latex was prepared by (1) vigorously mixing a cyclohexane solution of polymer and oil with a 1 / solution of a soap, prepared by neutralizing disproportionate rosin with potassium hydroxide to pH 10.5 - 11.0, (2) of the cyclohexane and (3) centrifuging in and for concentrating the latex into. about 65 wt / solids.

Glue joints were made by coating 2.54 cm wide canvas strips with the latex and compressing the strips in a heated press at 125 ° C to give contact surfaces 2.54 x 2.54 cm. The cohesive strength of shear was determined by pulling the joint with an Instron Tester, (Instron Corporation, Corporate II.Q., 2500 Washington Street, Massachusetts, US.) At 5 µm / min, to failure. The maximum stress thus obtained is given as the cohesive strength.

__. - The segment polymer used was a polystyrene-polyisoprene-polystyrene segment polymer with segment molecular weights 72,000, 92,000 and 77,000, respectively. The styrene content was 62 wt /. The oil was of the type listed under A in Table 1. The resin was Poly Pale Ester-10, which is described in Example 1. The mixture of the binder on an aqueous and soap-free base is given below, together with the test results:

Composition (anhydrous), parts by weight. Segment polymerisate · 100

Oil 75

Resin 100

Stabilizer (as in Table 1) 1

Test Results

Cohesion strength, shear force in kp for an overlap joint 2.54 x 2.54 cm 128

Peel / canvas peeling strength (cohesion strength burst limit) kp / 2.54 cm 5.67

Example IV /

A substantially saturated, hydrogenated, segmented polymer polymer having the polystyrene-polybutadiene-polystyrene molecular weight structure prior to hydrogenation 15,000 - 75,000 - 15,000 was dissolved in toluene to a 20% solution. Varying amounts of a naphthenic excipient oil and a polymerized terpene resin to increase stickiness were added and the solution was stirred to homogeneity. Samples were prepared by smearing films on glass and drying in nitrogen. 2.54 cm wide canvas strips are coated and dried several times, overlapping 2.54 x 2.54 cm, after which the joints are easily compressed at room temperature and dried for 24-76 hours at room temperature and under pressure in a nitrogen atmosphere. The results obtained are summarized in the following table:

<td>. a) ) well,</td><td>Oil ^b),</td><td>Stickiness (Hercules Thank You) for a probe with diam. 1.6 mm</td><td>Shear cohesion strength for an overlap joint in kp / 2.54 cm width</td>

<td> 50</td><td> 75</td><td> 650</td><td> 54,4</td>

<td> 50</td><td> 50</td><td> 400</td><td> 79,4</td>

<td> 50</td><td> 150</td><td>I650</td><td> 9,75</td>

<td> 25</td><td> 75</td><td> 1000</td><td> 90,7</td>

<td> 75</td><td> 150</td><td> 1475</td><td> 13,6</td>

(a) naphthenic excipient oil

b) polymerized terpenes

From the data given in the table, it can be seen that these mixtures have excellent tackiness and cohesion strength.

Example V

The segment polymers used in this example were poly (2-vinylpyridine) -polybutadiene-poly (2-vinylpyridine) with segment molecular weights 10,000 - 75,00010,000. This polymer was treated in the manner set forth in the preceding example.

326294 ₁₂ Except that the solvent has been modified with a sufficient amount of ethyl ethyl ketone to obtain a clear solution. With this mixture was carried out

<td>the following tests: Oil ^a), %</td><td>* * Oil ^b) $</td><td>Stickiness (Hercules Thank You) for a probe with diam. 1.6 mm</td><td>Shear cohesion strength for an overlap joint in kp / 2.54 cm width</td>

<td> 50</td><td> 100</td><td> . 1400</td><td> 9,55</td>

<td> 50</td><td> 50</td><td> 1050</td><td> 89,4</td>

<td> 50</td><td> 150</td><td> 650</td><td> 18,1</td>

<td> 25</td><td> 100</td><td> 400</td><td> 59,5</td>

<td> 75</td><td> 150</td><td> 1100</td><td> 25,1</td>

<td>a) naphthenic</td><td>oil</td><td></td><td></td>

<td colspan="3">b) polymerized terpene resin</td><td></td>

<td colspan="2">Of the ones listed in the table</td><td colspan="2">data show that this polymer provides</td>

<td colspan="2">sticky adhesive blends with</td><td>excellent tackiness</td><td>and cohesive strength.</td>

The presence of polar radicals in the molecule results in excellent adhesion strength to polar or metallic surfaces.