Primer compositions for adhesives

Abstract

A primer comprises a carrier and compound (II), wherein R7 to R11 are independently selected from H, OH, halogen, CH3, linear or branched C2-C6 alkyl, linear or branched C2-C6 alkoxy, linear or branch

Description

Field

[0001] The present invention relates to primer compositions. Of particular interest are primer compositions for plastics such as for polyamides. Of interest are primer compositions for substrates to be bonded with acrylic adhesives. Description of Related Art

[0002] It is widely known in the field of adhesives and polymers that certain substrates are difficult to bond. This can arise due to properties related to their surface chemistry such as low surface energy and / or low surface tension.

[0003] Various strategies have been developed to bond such materials with poor / incompatible surface properties. Surface treatment is frequently used to enhance the strength of the bonding between two surfaces and usually involves the surface of the substrate being physically roughened prior to bonding. This is easily achieved by treatment of the substrate with acid or some form of abrasion. Additionally, or alternatively, adhesive compositions have been specifically formulated to bond such substrates with poor surface energy properties, and more recently surface specific primers have been developed to facilitate enhanced bonding between low surface energy substrates. Priming the surface of the substrate prior to bonding alters the physical surface properties of the substrate and facilitating stronger binding between substrates.

[0004] A wide range of methods are known for joining two or more substrates together of a similar nature. In this case, methods such as infrared welding, infrared / friction welding, ultrasonic welding or hot plate welding. However, when two substrate materials that are mutually incompatible are to be welded together, it is typically not possible to produce a lasting connection between the two substrates that has a sufficiently high mechanical strength. In the event of an attempt being made to directly weld two different polyamide plastics using a welding method known from the prior art, usually very low and inadequate strengths are obtained.

[0005] Thus far, it has been possible to interconnect corresponding different polyamide plastics only by means of a mechanical connection or an adhesive bonding method in order to achieve high bonding strengths. Mechanical connection can often be complicated and cumbersome, while adhesive bonding often requires long periods of time to achieve final bonding strength. Furthermore, adhesively bonding low-energy surfaces usually requires laborious pre-treatments of the substrates. Providing a clean adhesive connection can also often be complex and time-consuming.

[0006] Notwithstanding existing solutions which address these issues, it is desirable to provide alternative solutions so the end user has more choices available. Summary

[0007] The present invention provides a composition, method, and use of a composition as set out in the claims. 12 01 26

[0008] The present invention relates to a primer composition which comprises a solution of an aromatic compound in a carrier such as a solvent, which may be an alcohol, for example iso-propyl alcohol (IPA). This primer composition can be applied to plastics substrates such as polyamides. The substrates can be subsequently bonded together, for example using an acrylic adhesive. The application of a primer composition of the invention to at least one of substrates to be bonded results in improved bond strengths, for example between the polyamide substrate(s) and acrylic adhesive.

[0009] It will be appreciated that only one of the substrates to be bonded together may be a difficult to bond substrate.

[0010] It will be appreciated that the primer composition can be applied to the surface of one or both substrates using any suitable method. The primer composition can be applied either to just one of surface of one or both substrates to be bonded together.

[0011] The present invention relates to a primer composition for an adhesive composition wherein the primer composition comprises: (i) a carrier for a primer component; and (ii) at least one primer component which is selected from among the compounds OH or OH

[0012] Optionally the carrier is a solvent for the primer component.

[0013] The carrier may be an alcohol for example, isopropyl alcohol.

[0014] The at least one primer component of the primer composition of the present invention is selected from the group consisting of: 12 01 26

[0015] The invention also relates to a method of bonding first and second substrates to each other, the substrates having respective bonding surfaces to be bonded together, the method comprising: (i) applying, to the bonding surface of at least the first substrate, a primer composition for an adhesive composition according to the invention to form a primed surface; (ii) applying an adhesive to: the primed surface; the bonding surface of the second substrate; or both the primed surface and the bonding surface of the second substrate; and (iii) mating the bonding surfaces.

[0016] Optionally the first substrate is a polyamide. In some embodiments of the method of the invention, the first substrate is a polyamide, and optionally wherein the second substrate is the same or a different polyamide.

[0017] Within the present invention at least one substrate may be a thermoplastic polyamide.

[0018] The polyamide may be selected from the group consisting of polyamide 6, polyamide 6.6, polyamide 6.10, polyamide 6.12, polyamide 9T, polyamide 10.10, polyamide 11, polyamide 12, polyamide 10.12, polyphthalamides, and / or combinations thereof. Of particular interest are optically transparent / UV transmissive plastics such as optically transparent / UV transmissive polyamides. Such substrates are of particular interest where they transmit LIV radiation and the adhesive (forming the bond) to be cured is UV-curable. In such a case, radiation, such as UV radiation, can be transmitted through the substrate to effect cure.

[0019] The primer composition of the invention may be used to prime a substrate, such as a polyamide substrate, for subsequent bonding with an acrylic adhesive. The adhesive may be a two-component adhesive such as a two-component acrylic adhesive. Detailed Description

[0020] Suitable adhesives for use with the primer composition of the present invention include but are not limited to anaerobic adhesives including acrylic anaerobic adhesives such as hydroxyethyl methacrylate, polyethylene glycol dimethacrylate, hydroxypropyl methacrylate, ethoxylated bisphenol A dimethacrylate, and urethane acrylates.

[0021] Suitable adhesives for use with the primer composition of the present invention may further include adhesive compositions, optionally in a two-part configuration comprising: a) Part (A) comprising a (meth)acrylate component, an organic peroxide and an acetal-containing free radically curable component; and b) Part (B) comprising a (meth)acrylate component, and benzoylthiourea derivatives or benzoylthiourethane derivatives.

[0022] The adhesive compositions, optionally in two-part configuration, suitable for use with the primer composition of the present invention optionally further comprise an acetalcontaining free radically curable component is represented by compounds within the general structure below: 12 01 26 wherein R1 is H, CH3 or CN; R2 is a multivalent Ci to Cs alkyl chain, Ceto C12 aryl group or Cato Cs cycloalkyl group; and n is 1-4.

[0023] The adhesive compositions, optionally in two-part configuration, suitable for use with the primer composition of the present invention may further comprise an acetal-containing free radically curable component is represented by compounds within the general structure below: wherein R1 is R1 is Ci to C30 alkyl, Cs to Csoaryl, ester, or carbamate; and R2 is a divalent unsaturated C2-C40 linkage (such as may be derived from a dicarboxylic acid selected from maleic acid, fumaric acid, itaconic acid, glutaconic acid, traumatic acid, glutinic acid and mesaconic acid).

[0024] The adhesive compositions, optionally in two-part configuration, suitable for use with the primer composition of the present invention may further comprise an acetal-containing free radically curable component is represented by compounds within the general structure below: 12 01 26 Cfk Q 0 GH- X 11 A '0' 'o' rs' o' '0' n \--- G . / X Xf' R1 wherein R1 is Ci to Csalkyl, Ceto C12 aryl or Cato Cs cycloalkyl; and R2 is a divalent unsaturated C2-C60 linkage.

[0025] The adhesive compositions, optionally in two-part configuration, suitable for use with the primer composition of the present invention may further comprise an acetal-containing free radically curable component wherein R2 of the acetal-containing free radically curable component is derived from a tricarboxylic acid selected from citric acid, isocitric acid, aconitic acid and trimesic acid.

[0026] The adhesive compositions, optionally in two-part configuration, suitable for use with the primer composition of the present invention may further comprise an acetal-containing free radically curable component which is represented by the compounds selected from the group consisting of:

[0027] The adhesive compositions, optionally in two-part configuration, suitable for use with the primer composition of the present invention may further comprise a (meth)acrylate component of at least one of the Part (A) or the Part (B) is selected from the group consisting of methyl (meth) acrylate, (meth)acrylic acid, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, cyclohexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, phenyl (meth)acrylate, tolyl (meth)acrylate, benzyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 12 01 26 stearyl (meth)acrylate, glycidyl (meth)acrylate, 2-aminoethyl (meth)acrylate, y-(meth)acryloyloxypropyl trimethoxysilane, (meth)acrylic acid-ethylene oxide adduct, trifluoromethylmethyl (meth)acrylate, 2-trifluoromethylethyl (meth)acrylate, 2-perfluoroethylethyl (meth)acrylate, 2-perfluoroethyl-2-perfluorobutylethyl (meth)acrylate, 2-perfluoroethyl (meth)acrylate, perfluoromethyl (meth)acrylate, diperfluoromethylmethyl (meth)acrylate, 2-perfluoromethyl-2-perfluoroethylmethyl (meth)acrylate, 2-perfluorohexylethyl (meth)acrylate, 2-perfluorodecylethyl (meth)acrylate, 2-perfluorohexadecylethyl (meth)acrylate, ethoxylated trimethylolpropane triacrylate, trimethylol propane trimethacrylate, di pentaery th ri to I monohydroxypentacrylate, pentaerythritol triacrylate, ethoxylated trimethylolpropane triacrylate, 1,6-hexanedioldiacrylate, neopentyl glycoldiacrylate, pentaerythritol tetraacrylate, 1,2-butylene glycoldiacrylate, trimethylopropane ethoxylate tri(meth)acrylate, glyceryl propoxylate tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, di pentaerythritol monohydroxy penta(meth)acrylate, tri(propylene glycol) di(meth)acrylate, neopentylglycol propoxylate di(meth)acrylate, 1,4-butanediol di(meth)acrylate, polyethyleneglycol di(meth)acrylate, triethyleneglycol di(meth)acrylate, butylene glycol di(meth)acrylate, ethoxylated bisphenol A di(meth)acrylate, and combinations thereof.

[0028] The adhesive compositions, optionally in two-part configuration, suitable for use with the primer composition of the present invention may further comprise a benzoylthiourea derivatives or benzoylthiourethane derivatives which are represented by compounds within the general structure below: wherein Z is O or N-R, where R is selected from hydrogen, Ci-Ce alkyl, C2-C6 alkenyl, Ci-Ce hydroxyalkyl, C2-C6 hydroxyalkenyl, carbonyl, alkylene (meth)acrylate, carboxyl, or sulfonato, or R’ is a direct bond attaching to the phenyl ring; R’ is selected from hydrogen, Ci-Ce alkyl, C2-C6 alkenyl, C3-C9 cycloalkyl, C3-C9 aryl, C2-C6 hydroxyalkyl, C2-C6 hydroxyalkenyl, C2-C6 alkylene- or alkenylene-ether, carbonyl, alkylene (meth)acrylate, carboxyl, nitroso or sulfonato; X is halogen, Ci-Ce alkyl, C2-C6 alkenyl, Ci-Ce hydroxyalkyl, C2-C6 hydroxyalkenyl, Ci-Ce alkoxy, amino, carboxyl, nitroso, sulfonate, hydroxyl or C2-C6 haloalkyl; and Y is -SO2NH-, -CONH-, -NH-, and -PO(NHCONHCSNH2)NH-; and n is 0 or 1 and m is 1 or 2; or (IA) 12 01 26 wherein R and R’ are independently selected from hydrogen, Ci-Ce alkyl, alkenyl C2-C6, C3-Csaryl, Ci-Cehydroxyalkyl, C2-C6hydroxyalkenyl, C2-C6 alkylene (meth)acrylate, carbonyl, carboxyl, or sulfonato, or R and R’ taken together form a carbocyclic or hetero atomcontaining ring, or R’ is a direct bond attaching to the phenyl ring; X is halogen, Ci-Ce alkyl, C2-C6 alkenyl, C3-C9 cycloalkyl, Ci-Ce hydroxyalkyl, C2-C6hydroxyalkenyl, Ci-Ce alkoxy, amino, Ci-Ce alkylene- or alkenylene-ether, Ci-Ce alkylene (meth)acrylate, carbonyl, carboxyl, nitroso, sulfonate, hydroxyl or haloalkyl; and Y is -SO2NH-, -CONH-, -NH-, and -PO(NHCONHCSNH2)NH-; and n is 0 or 1 and m is 1 or 2.

[0029] The adhesive compositions, optionally in two-part configuration, suitable for use with the primer composition of the present invention may further comprise a benzoylthiourea derivatives or benzoylthiourethane derivatives which are represented by compounds within the general structure below: Wherein R, X, Y, and n are defined above and X’ is defined as X.

[0030] The adhesive compositions, optionally in two-part configuration, suitable for use with the primer composition of the present invention may further comprise a benzoylthiourea derivatives or benzoylthiourethane derivatives which are represented by compounds within the general structure below: (IV) 12 01 26 Wherein R, R’, X, Y and n are as defined above, and m is 2.

[0031] The adhesive compositions, optionally in two-part configuration, suitable for use with the primer composition of the present invention may further comprise a block copolymer.

[0032] The adhesive compositions, optionally in two-part configuration, suitable for use with the primer composition of the present invention may be prepared by the method comprising: (a) forming Part (A) comprising a (meth)acrylate component, an organic peroxide and an acetal-containing free radically curable component; and (b) forming Part (B) comprising a (meth)acrylate component, and benzoylthiourea derivatives or benzoylthiourethane derivatives.

[0033] The adhesive compositions, optionally in two-part configuration, suitable for use with the primer composition of the present invention may be used in a method of bonding a first surface to a second surface, comprising: providing a two-part composition comprising: (a) Part (A) comprising a (meth)acrylate component, an organic peroxide and an acetal-containing free radically curable component; and (b) Part (B) comprising a (meth)acrylate component, and benzoylthiourea derivatives or benzoylthiourethane derivatives.

[0034] The adhesive compositions, optionally in two-part configuration, suitable for use with the primer composition of the present invention may be used for the method previously disclosed wherein when Part (A) and Part (B) are mixed and applied to at least one substrate, the composition will have up to 5 minutes of open time and when the substrates are mated they will have a cure time of about 20 minutes or less at 80 °C; and a fixture time of less than 5 minutes at which the bond will support 3Kg.

[0035] The adhesive compositions, optionally in two-part configuration, suitable for use with the primer composition of the present invention may be used for the method previously 12 01 26 disclosed wherein when Part (A) and Part (B) are mixed in a ratio of 1:10 to 10:1 Part (A) to Part (B) by volume.

[0036] The adhesive compositions, optionally in two-part configuration, suitable for use with the primer composition of the present invention may comprise: (a) a meth(acrylate) component; (b) a cure package comprising an organic peroxide and benzoylthiourea derivatives or benzoylthiourethane derivatives; and (c) an acetal-containing free radically curable component.

[0037] The adhesive compositions, optionally in two-part configuration, suitable for use with the primer composition of the present invention may further comprise a reactive acid component.

[0038] The adhesive compositions, optionally in two-part configuration, suitable for use with the primer composition of the present invention may further comprise a reactive acid component wherein the reactive acid component is (meth)acrylic acid.

[0039] The adhesive compositions, optionally in two-part configuration, suitable for use with the primer composition of the present invention may further comprise a reactive acid component wherein the reactive acid component is sulphonic acid or sulphonic acid derivatives, phosphoric acid, phosphoric acid derivatives, and phosphate esters, or acrylic acid. Examples

[0040] Eight compounds were investigated for their potential as primer components for the primer composition of the present invention as follows: (1) 4-hydroxybenzoic acid (2) orcinol (3) 1,3,5-trihydroxybenzene (4) 3-hydroxybenzoic acid, (5) 2,5-di hydroxy benzoic acid (6) 3,4,5-trihydroxbenzoic acid (7) 4-hydroxy-2-methylbenzoic acid; and (8) 4-fluoro-2-methylbenzoic acid. This numbering will be adhered to throughout the experiments below. It is noted that compounds (2) and (3) are compounds within the appended claims.

[0041] Each compound was tested individually as 5% w / w solutions in iso-propyl alcohol. The substrates were bonded with Loctite® AA 3295 and Loctite® AA V5004. Loctite® AA 3295 is a two-component acrylic adhesive Loctite® AA V5004 is a two-component acrylic adhesive that has a fixture time of 3 minutes and a shear strength of 21 N / mm2. The substrate(s) used to test the shear strength using was grit blasted mild steel. The bonds were made as a 0.5 inch (1.27 cm) overlap, lap shear bond and pulled to break at 2mm / min. Control experiments were conducted without a primer compound on bare substrates - no primer nor solvent was used. All experiments were conducted according ISO 4587 for the determination of tensile lap-shear strength of rigid-to-rigid bonded assemblies. The unit of measurement of shear strength in the tables below is N / mm2. 12 01 26 Table 1. Performance with Loctite® AA V5004 on PA6-PA6 Compound Control (1) (2) (3) (4) (5) (6) (7) (8) Average 1.18 4.72 4.99 4.59 4.80 4.88 3.51 4.50 2.93 Standard Deviation 0.18 0.32 0.50 0.48 0.37 0.80 0.57 0.54 0.39 Table 2. Performance with Loctite® AA V5004 on PA 9T-PA 9T Compound Control (1) (2) (3) (4) (5) (6) (7) (8) Average 1.89 2.73 6.34 2.53 4.35 5.88 1.20 3.60 2.08 Standard Deviation 0.18 0.33 1.09 0.19 0.51 0.74 0.39 0.49 0.37 Table 3. Performance with Loctite® AA 3295 on PA 6-PA 6 Compound Control (1) (2) (3) (4) (5) (6) (7) (8) Average 1.22 2.48 2.13 2.51 2.33 2.77 1.22 1.88 1.33 Standard Deviation 0.43 0.50 0.48 0.41 0.72 0.68 0.55 0.18 0.38 Table 4. Performance with Loctite® AA 3295 on PA 9T-PA 9T Compound Control (1) (2) (3) (4) (5) (6) (7) (8) Average 0.44 1.13 2.01 1.09 0.99 1.63 0.55 0.98 1.44 Standard Deviation 0.60 0.76 0.42 0.36 0.17 0.54 0.47 0.34 0.60 12 01 26

[0042] PA 6 is polyamide 6; so PA 6-PA 6 indicates both substrates are polyamide 6;

[0043] PA 9T is polyamide 9T; so PA 9T-PA 9T indicates both substrates are polyamide 9T.

[0044] The words “comprises / comprising” and the words “having / including” when used herein with reference to the present invention are used to specify the presence of stated features, integers, steps or components but do not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0045] It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination.

Claims

1. A primer composition for an adhesive composition wherein the primer composition comprises:(i) a carrier for a primer component; and(ii) at least one primer component which is selected from among the compoundsOH or OH23 06 252. A primer composition according to claim 1, wherein the carrier is a solvent for the primer component.

3. A primer composition according to any preceding claim, wherein the carrier is an alcohol.

4. A primer composition according to any preceding claim, wherein the carrier is isopropyl alcohol.

5. A primer composition according to any preceding claim, wherein the primer component is present at a concentration of 0.1-10 % by weight based on the total weight of the composition.

6. A method of bonding first and second substrates to each other, the substrates having respective bonding surfaces to be bonded together, the method comprising:(i) applying, to the bonding surface of at least the first substrate, a primer composition according to any of claims 1 to 5 to form a primed surface;(ii) applying an adhesive to: the primed bonding surface of the first substrate; the bonding surface of the second substrate; or both the primed bonding surface of the first substrate and the bonding surface of the second substrate; and(iii) mating the bonding surfaces.

7. A method of bonding according to claim 6 wherein the first substrate is a polyamide.

8. A method of bonding according to claim 6 or 7 wherein the first substrate is a polyamide, selected from the group of polyamide 6, polyamide 6.6, polyamide 6.10, polyamide 6.12, polyamide 9T, polyamide 10.10, polyamide 11, polyamide 12, polyamide 10.12, polyphthalamides, and / or mixtures thereof,,and optionally wherein the second substrate is the same or a different polyamide selected from the same group.

9. A method of bonding according to any of claims 6 to 8 wherein the adhesive is a two-component acrylic adhesive.

10. Use of at least one primer component which is selected from:23 06 25OH or OHin a primer composition for an adhesive composition for bonding a first substrate to a second substrate.