WO2019038324A1

WO2019038324A1 - A primer or adhesive coating composition

Info

Publication number: WO2019038324A1
Application number: PCT/EP2018/072661
Authority: WO
Inventors: Tommy HARALDSON; Henrik MIKAELSSON; Carl Fredrik Carlborg
Original assignee: MERCENE LABS AB
Current assignee: MERCENE LABS AB
Priority date: 2017-08-23
Filing date: 2018-08-22
Publication date: 2019-02-28
Anticipated expiration: 2020-02-23

Abstract

There is disclosed an initiator system for an epoxy primer or adhesive coating, the primer or adhesive coating composition comprising a polymerizable compound comprising at least one epoxide group,a polymerizable compound comprising at least one thiol group, and at least one quaternary ammonium salt and at least one heat-activated initiator which is a latent amine or amide, wherein the heat-activated initiator is inactive before heated to an activation temperature. Advantages include that the curing temperature is low while still having an acceptable curing time and the pot life is sufficiently long for the primer or adhesive coating to be very suitable for industrial applications.

Description

A PRIMER OR ADHESIVE COATING COMPOSITION

Technical field

The present invention relates generally to an epoxy-thiol primer made with an initiator system comprising an inactive latent nucleophile as well as a quaternary ammonium salt. More in detail, it relates to a primer or adhesive coating composition for epoxy-thiol systems and comprises an

initiator with a quaternary ammonium salt and a latent amine or amide curing agent. The composition is intended to be used as a coating where further coating (s) are to be applied onto the coating, i.e. as a primer coating or alternatively it is intended to be used as an adhesive.

Background

Primers are often used as an intermediate layer before another coating is applied on the primer coating. Adhesives are used as a layer between the surfaces of separate items for binding them together. For sensitive substrates, it is a problem that heating to rather high temperature has to be used to initiate a polymerization reaction in a coating.

Further it is a problem that the pot life a coating

composition may be too short to be useful. In particular, it is difficult to combine gentle hardening conditions and a long pot life. It is also desired to improve the adhesion to various substrates. Latent amine or amide curing agents are well known in the art for epoxy systems .

WO 2013/167576 discloses an object with a coating comprising: a) covalent bonds formed by reaction of a thiol group and a carbon-carbon double bond, b) covalent bonds formed by reaction of a thiol group and epoxide group, c) covalent bonds formed by a reaction of a carbon-carbon double bond and an epoxide group, said coating comprising a first primer coating and a second coating, said coating comprising

covalent bonds between said first and second coatings, said first primer coating comprising covalent cross links between compounds, in the first coating the fraction (r3 = ta/tc) of unreacted thiol groups (ta) to thiol groups which have reacted to form a covalent bond (tc) does not exceed 0.11.

WO 2012/042059 discloses a method for the manufacture of articles of thiol-ene polymers comprises the steps: a) reacting a compound comprising at least two thiol groups and a compound comprising at least two carbon-carbon double bonds, in off stoichiometry ratios to obtain a first

intermediate article, wherein said first intermediate article comprises at least one unreacted group selected from an unreacted thiol group and an unreacted carbon-carbon double bond, and b) contacting said first intermediate article with a second article, wherein the surface of said second article at least partially comprises reactive groups and reacting at least a part of said unreacted groups on said first

intermediate article with chemical groups on said second article to obtain covalent bonds and forming a final article.

US 4,173,476 discloses a photopolymerizable epoxy with a certain complex salt present. (A triarylsulfonium complex salt) A heat-induced polymerization is not disclosed.

US 6,166,101 discloses an initiator giving rise to a cation when irradiated with UV-light . A heat-activated initiator is not mentioned.

US 7,572,506 discloses a polyamine curing agent for the epoxy. Such curing agents are known to be heat-activated also at low temperature. It is mentioned curing at room temperature within 10 to 20 hours. Also 20 to 60 minutes at, for example, 40 to 80 °C. There is also disclosed the use as a primer. US 20100285309 discloses an epoxy which is cured with a heat- activated initiator. There is also disclosed use as a primer. Various salts may be present as a corrosion inhibitor. The initiator or curative may for instance be primary or

secondary amines. Polyamines are also mentioned. A curing time from about 1 second to about 14 days within the

temperature range of about 15 °C to about 250 °C is

disclosed. A shelf-stability of up to three months for 1 K Systems and up to 2 hours for 2K Systems under ambient temperature is mentioned. US 2010273005 discloses a heat curing epoxy composition with a hardener and an accelerant of a general Markush formula. Curing temperatures of 100-220 °C are mentioned.

WO 01/00698 discloses both two part and one part adhesive compositions. There are disclosed polyfunctional

mercaptoalkyl-substituted aryl compounds. The compounds include one or more aromatic rings, wherein at least one aromatic ring is substituted with at least one alkylthio group and at least one oxyalkylthio group. The adhesive systems include an epoxy resin or other compounds such as terminal olefins which are known to react with thiols.

Preferably, the compounds are used in combination with amine curatives as a two-component curing system for epoxy resins. Catalysts are also encompassed. In one embodiment a one component formulation is provided where the compositions are pre-mixed and partially cured before freezing them to stop the curing process. The curing continues when the composition is thawed and applied. The one-part adhesive has the drawback that it has to be frozen in order to halt the ongoing curing process until the curing is desired.

In the prior art there is a need for a coating which can be cured at low temperatures without any extended curing time, typically so low that sensitive substrates are not negatively affected and which has a long pot life so that it is

industrially applicable.

In particular there is a need for a primer or adhesive coating which is able to improve the adhesion, for instance for difficult substrates such as melamine.

It is desired to provide a one-component composition with extended pot-life which composition can be cured upon

activation and without any freezing. Summary

It is an object of the present invention to obviate at least some of the disadvantages in the prior art and to provide an improved primer or adhesive coating.

In a first aspect there is provided a primer or adhesive coating composition comprising a polymerizable compound comprising at least one epoxide group, a polymerizable compound comprising at least one thiol group, wherein the primer or adhesive coating composition comprises at least one quaternary ammonium salt and at least one heat-activated initiator which is a latent amine or amide, wherein the heat- activated initiator is inactive before heated to an

activation temperature.

Further aspects and embodiments are defined in the appended claims and the description. The invention is highly suitable for all applications where a coating is needed to improve the adhesion and other

properties. In particular, the adhesion is improved for known difficult substrates such as melamine. After extensive research it has turned out that the addition of a quaternary ammonium salt improves the adhesion especially for known difficult materials such as melamine, in particular when the curing temperature is not so high, i.e. well within the temperature limits mentioned in the application. In particular, the primer is suitable for sensitive

substrates, which cannot withstand heating to high

temperatures. In one embodiment, the temperature can be kept as low as 85 °C during curing. Still the composition has a long pot life of about 24 hours in one embodiment, which allows for many industrial coating applications. The curing at low temperature still has an acceptable curing time in spite of the low temperature.

Detailed description

Before the invention is disclosed and described in detail, it is to be understood that this invention is not limited to particular compounds, configurations, method steps,

substrates, and materials disclosed herein as such compounds, configurations, method steps, substrates, and materials may vary somewhat. It is also to be understood that the

terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting since the scope of the present invention is limited only by the appended claims and equivalents thereof.

It must be noted that, as used in this specification and the appended claims, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise .

The wording "primer or adhesive coating composition"

indicates the intended use for the composition. It is thus a composition that can be used to make a primer coating, or to make an adhesive coating. Thus, there is provided a coating composition that can be used both as a primer coating

composition and as an adhesive coating composition. The word coating includes all forms of application and dispensing to a surface.

If nothing else is defined, any terms and scientific

terminology used herein are intended to have the meanings commonly understood by those of skill in the art to which this invention pertains. In a first aspect there is provided a primer or adhesive coating composition comprising a polymerizable compound comprising at least one epoxide group, a polymerizable compound comprising at least one thiol group, wherein the primer or adhesive coating composition comprises at least one quaternary ammonium salt and at least one heat-activated initiator which is a latent amine or amide, wherein the heat- activated initiator is inactive before heated to an

activation temperature.

The heat-activated initiator should be inactive before heating to an activation temperature. The activation

temperature is the temperature to which the composition is heated when it is desired to initiate the curing. In the prior art the curing has been partially stopped by freezing the mixture. The initiator should be completely inactive in the one-component composition so as not contribute to any slow curing. Particular measures are needed to prevent the initiator from contributing to the curing before heating. In the present invention, the heat-activated initiator can be held inactive in several ways. In one embodiment, the heat- activated initiator is inactive before heated to an

activation temperature by being provided in the form of particles completely coated with a material adapted to melt at the activation temperature. The initiator is provided as particles, which particles are coated with a material that melts at the activation temperature so that the initiator is exposed to the surroundings and is able to initiate the curing reaction.

In one embodiment, the material adapted to melt at the activation temperature is wax. Such waxes are lipophilic malleable solids around room temperature. Waxes include higher alkanes and lipids. Waxes are insoluble in water but soluble in organic non-polar solvents. Thus, organic non- polar solvents should be avoided or at least not used to such an extent that they dissolve the coating of wax.

In one embodiment, the heat-activated initiator is inactive before heated to an activation temperature by being provided in an inactive crystalline form adapted to melt to an active form at the activation temperature. Some initiators are inactive or virtually inactive when in crystalline form, but when melted or in amorphous form, they are active. The crystals melt or change into amorphous structure when heated above the activation temperature.

In one embodiment the primer or adhesive coating composition comprises at least one compound increasing the pH .

Preferably, the pH of an aqueous solution of the components is above 7. In one embodiment, the pH is above 8. In one embodiment the primer or adhesive coating composition

comprises at least one compound increasing the pH, said at least one compound increases the pH at least during heating. In one embodiment the primer or adhesive coating composition comprises at least one compound increasing the pH at all temperatures at least to some extent. In an alternative embodiment the primer or adhesive coating composition

comprises at least one compound increasing the pH in

particular at elevated temperatures, i.e. during heating. The temperature during such heating is the same as when the primer or adhesive coating composition is heated to initiate the polymerization reaction. The heating to increase the pH is thus the same heating as when initiating the

polymerization reaction. The pH is important during the initiation of the polymerization reaction and thus it is sufficient that the pH is increased during the heating.

In an alternative embodiment the primer or adhesive coating composition comprises at least one compound lowering the pH, said at least one compound being adapted to evaporate during heating so that the pH increases. By this approach, the pH is also increased during heating but with aid of a compound evaporating during heating. In one embodiment, acetic acid is utilized as the evaporating compound so that the pH increases when it evaporates. This alternative approach is particularly suitable for thin films where evaporation is easy due to the large surface to bulk ratio.

In one embodiment the at least one heat-activated initiator is a latent amine. In one embodiment the at least one heat- activated initiator is amide. In one embodiment the at least one heat-activated initiator comprises both an amine and an amide. In one embodiment the at least one heat-activated initiator is a latent cycloaliphatic amine. In one embodiment the at least one heat-activated initiator is an imidazole.

In one embodiment the at least one quaternary ammonium salt is tetrabutylammonium acetate. In one embodiment the amount of the at least one quaternary ammonium salt is in the range 0.1 to 10 % of the weight of the total composition. In one embodiment the amount of the at least one quaternary ammonium salt is in the range 0.3 to 2 % of the weight of the total composition. In one embodiment the amount of the at least one heat- activated initiator is in the range 0.1 to 15 % of the weight of the total composition. Regarding calculation of the amount of the at least one heat-activated initiator, any coating adapted to melt at the activation temperature is included in the weight of the initiator. If the initiator for instance is provided as particles coated with a material adapted to melt at the activation temperature, then the coating material (such as wax) is included in the weight of the initiator. This facilitates the measuring of the initiator since the initiator is often provided from an external manufacturer in the form of coated particles. If the initiator for instance is provided as uncoated crystals or other inactive particles without coating, the initiator particles are weighed to determine the amount of initiator. In one embodiment, the relation between the amount of the polymerizable compound comprising at least one epoxide group, and the polymerizable compound comprising at least one thiol group is so that the total number of epoxide groups and the total number of thiol groups is about equal, i.e. a

stoichiometric ratio between the polymerizable compounds in the composition. I.e. the number of epoxy groups is the same as the number of thiol groups or at least within ±10% of the number of thiol groups. In one embodiment, the number of epoxy groups is within ±5% of the number of thiol. In another embodiment the number of epoxy groups is within ±1% of the number of thiol groups .

In an alternative embodiment, the ratio between the

polymerizable compounds in the composition is non- stoichiometric, i.e. total number of epoxide groups and the total number of thiol groups in the composition is not equal. In one embodiment, the number of epoxy groups is at least 10% higher than the number of thiol groups. In one embodiment the number of epoxy groups is from 10% to 50% higher than the number of thiol groups. A polymerizable compound may comprise more than one epoxide group, or more than one thiol group respectively. The number of epoxide or thiol groups in the composition is used to calculated the ratio between the amount of polymerizable compound comprising epoxide groups and, the amount of

polymerizable compound comprising epoxide groups.

In one embodiment the composition comprises a polymerizable compound comprising at least one carbon-carbon double bond. Additional monomer compounds are optional and can be added as needed to obtain the desired final polymerized product. In a second aspect there is provided a method of coating a substrate, said method comprising the steps of

• providing a substrate,

• applying a primer or adhesive coating composition to at least a part of the substrate, said primer or adhesive coating composition comprising a polymerizable compound comprising at least one epoxide group, a polymerizable compound comprising at least one thiol group, wherein the primer or adhesive coating composition comprises at least one quaternary ammonium salt and at least one heat-activated initiator which is a latent amine or amide, wherein the heat-activated initiator is inactive before heated to an activation temperature,

• initiating a polymerization reaction in at least a part of the applied primer or adhesive coating composition by heating .

The steps of the method are intended to be performed

sequentially. After the last step, i.e. the curing a primer or adhesive coating is formed. In one embodiment the polymerization reaction is complete and in an alternative embodiment the polymerization reaction is partial. In one embodiment the polymerization reaction is first partial and then the polymerization reaction is allowed to proceed to completion after a period of time.

In one embodiment the initiating is performed by heating to a temperature in the interval 75-120 °C. In one embodiment the initiating is performed by heating to a temperature in the interval 75-100 °C. In one embodiment the initiating is performed by heating to a temperature in the interval 80-95 °C. In one embodiment the initiating is performed by heating to a temperature in the interval 82-90 °C. In one embodiment the initiating is performed by heating to a temperature in the interval 83-89 °C. It is an advantage that the

temperature can be held relatively low so that temperature sensitive objects can be treated. In one embodiment the method comprises a further step d) applying at least one further coating on at least parts of the substrate. Since the primer is intended to be used with another coating on top, it is a natural step to apply a further coating, either directly after heating and curing of the primer or after an extended period of time.

In one embodiment the method comprises a further step of bringing another object in contact with at least a part of the applied primer or adhesive coating composition. The other object is brought into contact with the coating composition either before initiating a polymerization reaction or when the polymerization reaction has completed only partially so that the polymerization reaction can complete to achieve good adhesion between the substrate and the other object. When used as an adhesive one or both of the objects to be joined together are coated with the coating.

In one embodiment the substrate to be coated is a polymeric substrate .

In a third aspect there is provided a coated object, wherein the coated object is made according to the description above.

In a fourth aspect there is provided a kit of parts

comprising :

• a polymerizable compound comprising at least one epoxide group, · a polymerizable compound comprising at least one thiol group,

• an initiator comprising at least one quaternary ammonium salt and at least one heat-activated initiator which is a latent amine or amide, wherein the heat-activated initiator is inactive before heated to an activation temperature ,

• an instruction to use the parts of the kit as a primer or adhesive coating composition.

In one embodiment the kit of parts further comprises an instruction to heat a mixture of the components.

All embodiments of all aspects can be combined freely.

Other features and uses of the invention and their associated advantages will be evident to a person skilled in the art upon reading the description and the examples.

It is to be understood that this invention is not limited to the particular embodiments shown here. The embodiments are provided for illustrative purposes and are not intended to limit the scope of the invention since the scope of the present invention is limited only by the appended claims and equivalents thereof.

Examples

Method to determine pot life

The pot life is easily observed just by tilting the

respective bottles, since the viscosity increase for the tested formulations is rather sharp at the end of the pot life.

Method to determine low temperature cure properties

Apply two tape strips parallel and 10 mm apart on a

microscope glass slide. The tape thickness is approximately 30 microns. Apply a small amount of coating at one end of the glass slide. Spread the coating between the tape strips using a stainless steel doctor blade.

Put the sample on a hotplate set at 85 °C for 45 seconds. After the heating procedure, remove the sample and let it rest at ambient temperature. Use a spatula to determine when the coating has solidified. The development of a tack free surface can be felt by a fingertip preferably wearing a thin nitrile rubber glove. The result is measured as the time from the start of the test to the point where the coating is tack free.

Method to determine the Hamberger value

The Hamberger testing procedure is designed to evaluate the scratch resistance of coatings on wood or wood-based surfaces by using the Hamberger plane (behavior under scratching load from a curved, moderately sharp edge) . The determined values are given in Newtons [N] as "scratch resistance according to the Hamberger test. The method determines the resistance of a coated surface against abrasion by a narrow edge by

establishing the maximum weight force (=test force) that can be applied to an abrading edge (=test edge) without causing a noticeable change or damage to the coating. The Hamberger plane instrument consists of the following components: 1) Test blade made of carbide with a diameter of 12.75 mm at the cutting edge and a subsequently rounded edge, 2) Test edge, the segment of the cutting edge that is in contact with the test sample's surface during the test, 3) Rocker, a metal block for holding and fastening the test blade. It is

designed to allow moving the test blade at the specified angle (55 ⁰ with reference to the surface to be tested), 4) Loading device that allows the application of the test force to the test edge perpendicularly to the surface to be tested, 5) Housing that encloses the rocker and loading device described in previously.

Testing procedure followed the standard operating

instructions for the testing instrument: the samples to be tested were fixated horizontally, the Hamberger plane was placed on the sample, the test edge was lowered onto the surface and the loading device was set to the minimal test force to be expected, e.g. 10 N. The Hamberger plane was then pushed horizontally over the sample surface for a distance of about 200 mm (test path) . The path was then immediately inspected for damage. In this context, damage includes visible or noticeable deviations in color, as well as a partial or complete abrasion of the coating in the area of the test path over a continuous length of at least 2 mm and/or clusters. Indentation traces or shiny traces that do not deviate in color are not rated as damage. The test force was then increased and another test path is added and

inspected. The procedure was repeated until damage to the coating is observed. The result is calculated from a mean value from at least 3 test values for each surface that was tested . "

Resin formulation is equal in all experiments. All

percentages are calculated by weight. Component A

PENTAERYTHRITOL TETRAKIS ( 3-MERCAPTOBUTYLATE ) 70-90wt%

CAS No: 31775-89-0

PENTAERYTHRITOL TRIS ( 3-MERCAPTOBUTANOATE ) <20wt%

CAS No: 1027326-93-7 Component B

FORMALDEHYDE, OLIGOMERIC REACTION PRODUCTS WITH

l-CHLORO-2, 3-EPOXYPROPANE AND PHENOL 70-90wt%

CAS No: 9003-36-5

1, 3, 5, -TRIALLYL-1, 3, 5-TRIAZINE-2, 4, 6, (1H, 3H, 5H) -TRIONE

5-10wt%

CAS No: 1025-15-6

Optional remainder up to 100wt% is solvents.

1, 3, 5, -TRIALLYL-1, 3, 5-TRIAZINE-2, 4, 6, (1H, 3H, 5H) -TRIONE is not compulsory and the invention can be utilized without monomers comprising carbon-carbon double bonds. Components A and B were mixed by weight with 45 parts B and 100 parts of A. All parts are calculated by weight.

Initiators used

Ancamine 2441 is a modified polyamine designed for use as a latent curing agent for one-component adhesive formulations from Evonik®. It has a melting point about 124-135 °C and is provided as a powder with a particle size less than 10 pm. It is inactive in the provided form and becomes active upon heating. It is inactive in the provided form due to its crystalline structure . When heated it changes into an active structure .

LC-80, an encapsulated modified imidazole (amine) for one- component epoxy formulations from A&C Catalysts Inc®. The average particle size is 10 pm. It is encapsulated with wax and melts in the range of about 90-110 °C, thereby activating the initiator. TBAAc, tetrabutylammonium acetate from Sachem.

Formulations and results

Formulation 1 2 3 4 5 6 7 8 9 10 No

Comp A

100 100 100 100 100 100 100 100 100 100 parts

Comp B

45 45 45 45 45 45 45 45 45 45 parts

Ancamine

2441

5.91 5.91 5.91 11.8 5.91 11.8 5.91 parts

LC-80

2.96 2.96 2.96 2.96 5.92 5.92 2.96 parts

TBAAc

1.48 1.48 1.48 1.48 parts

Results

Pot life,

37 40 50 35 38 35 20 24 12 30 (h)

Time to tack

free film

70 >135 42 60 11 60 11 11 6 5

(min) All parts are calculated by weight. Conclusion

The heat latent amine or amide curing agents gives a

surprisingly good combination of pot life and low temperature cure. Such a combination is useful in many industrial

coatings and adhesive applications, for example roller coating .

Application examples

An HPL substrate formulation 10 (as described above) was applied using a 6 micron rod applicator and cured in a conveyor belt IR system. 2 minutes after exiting the conveyor belt system an acrylate base coat, UL1117 from Sherwin

Williams was applied using a 24 micron rod and cured with 500 mJ/cm² using a medium pressure Hg lamp.

Final temperature after IR 138 °C gave more than 30N

Hamberger value, 0 Crosshatch. Recorded 1 hour after cure.

Final temperature after IR 120 °C gave more than 30N

Hamberger value, 0 Crosshatch. Recorded 1 hour after cure.

Final temperature after IR 100 °C gave more than 20N

Hamberger value, 4 Crosshatch. Recorded 1 hour after cure.

Test of salt effect on a white high gloss HPL melamine

A high gloss white HPL foil glued on chip board was coated with a mixture comprising 100 weight-parts of component A, 45 weight-parts of component B, 5.91 weight-parts of Ancamine 2441 and 1.48 weight-parts of TBAAc . Another comparative mixture containing the same components except TBAAC was also prepared and coated similarly. All coatings were performed using a 6-micron rod-applicator. The room temperature HPL substrate was fed into an IR equipped with a conveyor belt reaching 97-99 °C in 20 s time. As soon as the panels had cooled to 50 °C, after around 60s, 13 microns of a hard base coat from Sherwin Williams was applied using a laboratory roller coater from Burkle, and the base coat was cured using a medium pressure mercury lamp equipped with a conveyor belt 1 pass at 8m/min setting to gel the layer and another 13 micron layer of UL 1117 was applied and subjected to UV light until it reached full cure after 4 passes at 8m/min. Adhesion was severely affected when no salt was used in the formulation .

Surprisingly, the pot life of the two formulations were similar at 16 hours despite the marked improvement in curing performance in the salt containing formulation. Normally, much improved curing reduces pot-life significantly.

Another application example

Hardening of a coating

Two stripes of tape were applied on a glass slide so that a surface area of about 15x75mm was obtained and with a depth of about 30pm. The substrate formulation 10 (as described above) was applied to this surface with a rod applicator. The slide was placed on a hot plate heated to the desired temperature. The applied liquid product was stirred with a spatula until it solidifies. The time until solidification was noted and thereafter the slide was allowed to cool to room temperature. Hardening of an adhesive

A few hundredths of one gram of the substrate formulation 10 (as described above) was placed centred on a glass slide. Another glass slide was placed on the applied substrate formulation in 90° angle compared to the first glass slide. The slide was placed on a hot plate heated to the desired temperature. The applied liquid product was carefully

subjected to shear forces by carefully twisting the upper glass slide. The time until solidification was noted and thereafter the slide was allowed to cool to room temperature. Results

Hardening of a coating, time to cure

70 °C 4 min

85 °C 1 min 35 s

100 °C 1 min 5 s

Hardening of an adhesive, time to cure

70 °C 4 min

85 °C 1 min 50 s

100 °C 1 min 0 s

Results It is shown that the same good reactivity is obtained both for open systems and enclosed systems.

The curing reaction is maintained until solidification.

Normally the curing reaction is driven further, but this is a comparison between the open (coating) and enclosed (adhesive) applications .

The samples were evaluated after 20 hours at room

temperature . A scratch test on the open (coating) samples shows that the 70 °C-sample is slightly softer compared to the other ones cured at higher temperatures.

A test for the enclosed (adhesive) samples gives that the glass breaks for all samples. The adhesive is thus stronger than the glass.

The curing initiation works at 70 °C but becomes better at 85 °C.

The pot life for the composition is sufficient. After 22 hours the viscosity has not changed according to the

following test. A half full 20 ml flask was put on its side and it took 20 seconds for the new surface to become flat. This did not change after 22 hours for the uncured

composition .

After 96 hours in room temperature the pot-life sample had cured. The hardness was 65 shore D. The same solution gave after curing in 100 °C and after-curing in 60 °C for 16 hours a hardness of 75 shore D as comparison.

Claims

1. A primer or adhesive coating composition comprising a polymerizable compound comprising at least one epoxide group, a polymerizable compound comprising at least one thiol group, characterized in that the primer or adhesive coating composition comprises at least one quaternary ammonium salt and at least one heat- activated initiator which is a latent amine or amide, wherein the heat-activated initiator is inactive before heated to an activation

temperature .

2. The primer or adhesive coating composition according to claim 1, wherein the heat-activated initiator is inactive before heated to an activation temperature by being provided in particles completely coated with a material adapted to melt at the activation temperature.

3. The primer or adhesive coating composition according to claim 2, wherein the material adapted to melt at the activation temperature is wax.

4. The primer or adhesive coating composition according to any one of claims 1-3, wherein the heat-activated

initiator is inactive before heated to an activation

temperature by being provided in an inactive crystalline form adapted to melt to an active form at the activation

temperature .

5. The primer or adhesive coating composition according to any one of claims 1-4, wherein the primer or adhesive coating composition comprises at least one compound

increasing the pH, said at least one compound increases the pH at least during heating.

6. The primer or adhesive coating composition according to any one of claims 1-5, wherein the primer or adhesive coating composition comprises at least one compound lowering the pH, said at least one compound being adapted to evaporate during heating so that the pH increases.

7. The primer or adhesive coating composition according to any one of claims 1-6, wherein the at least one heat- activated initiator is a latent cycloaliphatic amine.

8. The primer or adhesive coating composition according to any one of claims 1-6, wherein the at least one heat- activated initiator is an imidazole.

9. The primer or adhesive coating composition according to any one of claims 1-8, wherein the at least one quaternary ammonium salt is tetrabutylammonium acetate.

10. The primer or adhesive coating composition

according to any one of claims 1-9, wherein the amount of the at least one quaternary ammonium salt is in the range 0.1 to 10 % of the weight of the total composition.

11. The primer or adhesive coating composition

according to any one of claims 1-10, wherein the amount of the at least one heat-activated initiator is in the range 0.1 to 15 % of the weight of the total composition.

12. The primer or adhesive coating composition

according to any one of claims 1-11, wherein composition comprises a polymerizable compound comprising at least one carbon-carbon double bond.

13. A method of coating a substrate, said method

comprising the steps of a) providing a substrate, b) applying a primer or adhesive coating composition to at least a part of the substrate, said primer or adhesive coating composition comprising a polymerizable compound comprising at least one epoxide group, a polymerizable compound comprising at least one thiol group,

characterized in that the primer or adhesive coating composition comprises at least one quaternary ammonium salt and at least one heat- activated initiator which is a latent amine or amide, wherein the heat-activated initiator is inactive before heated to an activation temperature, c) initiating a polymerisation reaction in at least a part of the applied primer or adhesive coating composition by heating.

14. The method according to claim 13, wherein the initiating is performed by heating to a temperature in the interval 75-120 °C.

15. The method according to any one of claims 13-14, wherein the method comprises a further step d) applying at least one further coating on at least parts of the substrate.

16. The method according to any one of claims 13-14, wherein the method comprises a further step of bringing another object in contact with at least a part of the applied primer or adhesive coating composition.

17. A coated object, wherein the coated object is made according to the method of any one of claims 13-16.

18. A kit of parts comprising: a polymerizable compound comprising at least one epoxide group, a polymerizable compound comprising at least one thiol group, an initiator comprising at least one quaternary ammonium salt and at least one heat-activated initiator which is a latent amine or amide, wherein the heat-activated initiator is inactive before heated to an activation temperature, an instruction to use the parts of the kit as a primer or adhesive coating composition.

19. The kit of parts according to claim 18, wherein the kit of parts further comprises an instruction to heat a mixture of the components.