WO2019185697A1

WO2019185697A1 - Acrylate based coating with added thiol

Info

Publication number: WO2019185697A1
Application number: PCT/EP2019/057700
Authority: WO
Inventors: Tommy Haraldsson; Henrik MIKAELSSON; Carl Fredrik Carlborg
Original assignee: Mercene Labs Ab
Priority date: 2018-03-27
Filing date: 2019-03-27
Publication date: 2019-10-03

Abstract

There is disclosed an acrylate primer coating with a small amount of added thiol. More in detail the coating composition comprises at least one compound comprising at least one (meth)acrylate group and said coating composition comprising at least one compound comprising at least one thiol group. Advantages of the invention includes that the resistance towards high shear-impact wear is improved. Further the shelf life of the coating composition is improved.

Description

ACRYLATE BASED COATING WITH ADDED THIOL

Technical field

The present invention relates generally to an acrylate coating with thiol. A further coating, a top coating may or may not be applied on the acrylate coating. In particular, it relates to a coating system improving the resistance to shear impact and also polymerization shrinkage stress by using a thiol additive. More specifically, it is suitable for improving the resistance to marks resulting from high shear- impact wear on flexible materials such as polymeric floor coverings and high shear forces imparted during release of structures from imprinting tools. The coating is also suitable where an extended shelf life is desired.

Background

Coatings are often applied on flexible materials including polymeric materials. One example is PVC suitable for flooring applications . Acrylate coatings used today can be improved regarding for instance flexibility, adhesion, resistance to marks resulting from high shear-impact wear, and impact resistance. Primers are used as a coating under another coating in order to improve properties of the coating such as for instance adhesion, durability, and protection. Primers or undercoatings are preparatory coatings to be applied to a surface before coating with another coating. The coating applied on a primer is a sealer followed by a top coating or directly a top-coating.

Regarding high shear-impact wear, it is important to distinguish it from other types of wear such as scratches and similar types of mechanical wear. High shear-impact wear occurs when a shear force is applied to the surface and does not lead to the same effect as scratches. The scratch resistance is a surface phenomenon, whereas the resistance against high shear-impact wear depends on cohesion and the ability of the coating to absorb energy from the shear force, US 2007/0021521 discloses curable thiol-ene compositions containing urethane (meth) acrylate oligomers that are readily polymerized to produce optical articles and coatings.

US 2016/0222217 discloses scratch-resistant coatings obtained by reaction of (meth) acrylates and mercapto groups. The invention relies on phase separation where thiol (mercapto groups) are accumulated on the surface, which give good scratch resistance. The resistance against high shear-impact wear is thus not affected to any significant extent since the effect is concentrated to the surface and does not affect the bulk properties of the coating. Improvement of the resistance against high shear-impact wear has to do with bulk properties such as the ability to absorb mechanical force.

US 2016/0168416 discloses a two-component system, which according to one example hardens in room temperature during many hours making it unpractical for many industrial

applications .

A problem in the prior art is to lower the internal stresses in the coating and to increase the energy that can be absorbed by the coating form shear force. This will increase the resistance against high shear-impact wear.

Another problem in the prior art is to provide a composition with a long shelf life so that it can be utilized without difficulties within industry. A one-component system with a long shelf life is suitable from an industrial point of view. Another similar problem in the prior art is the release of thin films from the roller in UV nanoimprinting lithography, where a strong shear force is applied on the polymerized coating when it releases from the roller, in particular when it contains structures with high aspect ratio. Decreasing the internal stress and increasing the resistance towards shear- impact wear will reduce damages to the coated layer when it is abruptly released from the roller.

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 acrylate coating.

In a first aspect there is provided a coating composition, said coating composition comprising at least one compound comprising at least one (meth) acrylate group and said coating composition comprising at least one compound comprising at least one thiol group, wherein the ratio between the total number of thiol groups in the composition and the total number of (meth) acrylate groups in the composition is in the interval 0.01-0.3, said coating composition comprises at least one compound adapted to initiate a polymerization reaction between the at least one compound comprising at least one (meth) acrylate group and the at least one compound comprising at least one thiol group. Further aspects and embodiments are defined in the appended claims .

The invention is highly suitable for applications where a polymeric object is to be coated with a coating displaying a high resistance towards shear impact. This type of strain occurs in several situations. One example is marks resulting from high shear-impact wear, for instance on floor coverings. Another example is when an embossed material is removed from a master surface. The flexibility of the coating is improved, the impact resistance is improved, the tendency to leave marks resulting from high shear-impact wear is reduced and the adhesion is improved compared to acrylate coatings according to the state of the art, The invention is also suitable for thin films to be released from a master for instance within UV nanoimprinting

lithography, since a similar high shear impact occurs in such applications ,

A long shelf life is obtained for the coating composition, which is suitable and desirable for all industrial

applications ,

Brief description of the drawings

The invention is now described, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a bending/thickness ratio for compositions with different amounts of thiol groups as detailed in the examples. The Y-axis shows the ratio bending/thickness in pm³/g

Figure 2 shows damage to a surface after a pull test assay for different amounts of thiol for a one-layer system. The pull test is determined according to the scale described in the examples , Figure 3 shows damage to a surface after a pull test assay for different amounts of thiol for a different system, a two- layer system. The same scale as in fig 2 is used for

describing the surface. Figure 4 shows examples of embodiments, where (A) is a substrate (Examples of substrates include but are not limited to substrates comprising PVC, PET, rubber, metal, silicon, cellulose based and glass) , (B) is an unstructured layer of the presently disclosed coating, (C) is an embossed layer of the presently disclosed coating forming micro- and/or nano structures, (D) is a further coating applied on top of (B) , and (E) is a thin coating - relative the embossed structures - applied on top of the embossed structures (C) . (D) and (E) can be various further coatings as described. Examples of such further coatings include but are not limited to a metal coating, an inorganic coating and an organic coating.

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 . 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, As used herein (meth) acrylate is a general term that

encompasses both acrylate and methacrylate. At least one compound comprising at least one (meth) acrylate group then encompasses a compound comprising one or more (meth) acrylate groups, a compound comprising one or more methacrylate groups, and a compound comprising both (meth) acrylate groups and methacrylate groups.

Shear-impact is an impact (high force over a short period of time) resulting from a force coplanar with a material cross section. For a coating, it is associated with a force essentially in the plane of the surface to which the coating is applied.

Shear-impact wear is wear resulting from shear impact. For instance this occurs when pushing an object against a surface with a force and simultaneously moving the object on the surface. The object is then softer than the surface so that the object does not scratch the surface. This type of wear is often a problem on flooring applications where objects on the floor are moved in this way. Although an object moved on the floor is softer it may still cause shear-impact wear. High shear-impact wear denotes a relatively high wear in a relative sense. The wear is so high that it is a problem for many flooring applications including for instance PVC-floors . Shear-impact wear should not be confused with scratches and similar surface related phenomena. A scratch is caused by a harder object scratching a softer object. Shear-impact wear is related to the mechanical bulk properties of the coating film. Shear impact wear is associated with the ability of the coating to take up the shear impact. For scratches a harder object makes a scratch in a softer object, i.e. the surface which is scratched has a lower hardness measured according to Mohs compared to the object causing the scratch. For shear- impact wear the situation is the opposite. The surface is harder compared to the object making the shear impact. The surface has a higher hardness on the Mohs scale compared to the object causing the shear-impact. Shear-impact also occurs for instance, when a thin

(relatively soft) film is removed from a (relatively hard) surface to which it adheres. One example is when a coating is applied to a patterned master surface and subsequently removed after curing to form embossed structures. During the removal, the film is subjected to shear-impact, which may result in shear-impact wear or other undesired negative effects .

In a first aspect there is provided a method for improving the resistance towards shear-impact wear comprising applying a coating composition said coating composition comprising at least one compound comprising at least one (meth) acrylate group and said coating composition comprising at least one compound comprising at least one thiol group, wherein the ratio between the total number of thiol groups in the composition and the total number of (meth) acrylate groups in the composition is in the interval 0.01-0.3, said coating composition comprises at least one compound adapted to initiate a polymerization reaction between the at least one compound comprising at least one (meth) acrylate group and the at least one compound comprising at least one thiol group. It is conceived that the coating composition is a one component system which can be handled, stored and applied as one composition before the polymerization reaction is initiated. The one component system together with the excellent storage properties makes the composition suitable for most industrial applications.

In order to calculate the ratio between the thiol groups and (meth) acrylate groups, the total number of thiol groups n_t in the composition is counted and the total number of both methacrylate groups and acrylate groups n_a groups in the composition is calculated. Then the ratio n_t/n_a is

calculated, I.e. the ratio is based on numbers of groups. The total number of thiol and {meth) acrylate groups present in the composition is calculated, (meth) acrylate groups refers to methacrylate groups and acrylate groups, I.e. if other additives are present comprising such groups these groups should also be included in the calculation.

The initiator, i.e. the at least one compound adapted to initiate a polymerization is any suitable initiator. Examples include but are not limited to thermal initiators, and photoinitiators. Photoinitiators work together with actinic radiation to initiate a polymerization reaction. In one embodiment, a photoinitiator suitable for a wavelength in the UV-area is utilized, an UV-initiator . In one embodiment, the ratio between the total number of thiol groups in the composition and the total number of (meth) acrylate groups in the composition is in the interval 0.01-0.025.

In one embodiment, the ratio between the total number of thiol groups in the composition and the total number of (meth) acrylate groups in the composition is in the interval

0.04-0.1.

In one embodiment, the lower limit of the interval for the ratio between the total number of thiol groups in the composition and the total number of (meth) acrylate groups in the composition is 0.01. In one embodiment, the lower limit of the interval for the ratio between the total number of thiol groups in the composition and the total number of (meth) acrylate groups in the composition is 0.015. In one embodiment, the lower limit of the interval for the ratio between the total number of thiol groups in the composition and the total number of (meth) acrylate groups in the composition is 0.018. In one embodiment, the lower limit of the interval for the ratio between the total number of thiol groups in the composition and the total number of

(meth) acrylate groups in the composition is 0.02. In one embodiment, the lower limit of the interval for the ratio between the total number of thiol groups in the composition and the total number of (meth) acrylate groups in the composition is 0.03. In one embodiment, the lower limit of the interval for the ratio between the total number of thiol groups in the composition and the total number of

(meth) acrylate groups in the composition is 0.04.

In one embodiment, the upper limit of the interval for the ratio between the total number of thiol groups in the composition and the total number of (meth) acrylate groups in the composition is 0.098. In one embodiment, the upper limit of the interval for the ratio between the total number of thiol groups in the composition and the total number of (meth) acrylate groups in the composition is 0.1. In one embodiment, the upper limit of the interval for the ratio between the total number of thiol groups in the composition and the total number of (meth) acrylate groups in the composition is 0.15. In one embodiment, the upper limit of the interval for the ratio between the total number of thiol groups in the composition and the total number of

( eth) acrylate groups in the composition is 0,2, In one embodiment, the upper limit of the interval for the ratio between the total number of thiol groups in the composition and the total number of (meth) acrylate groups in the composition is 0.25. In one embodiment, the upper limit of the interval for the ratio between the total number of thiol groups in the composition and the total number of

(meth) acrylate groups in the composition is 0.3.

Thus different examples of intervals for the ratio between the total number of thiol groups in the composition and the total number of (meth) acrylate groups in the composition include but are not limited to 0.01-0.098, 0.01-0.1, 0.01- 0.15, 0.01-0.2, 0.01-0.25, 0.01-0.3, 0.015-0.098, 0.015-0.1, 0.015-0.15, 0.015-0.2, 0.015-0.25, 0.015-0.3, 0.018-0.098, 0.018-0.1, 0.018-0.15, 0.018-0.2, 0.018-0.25, 0.018-0.3,

0.02-0.098, 0.02-0.1, 0.02-0.15, 0.02-0.2, 0.02-0.25, 0.02- 0.3, 0.03-0.098, 0.03-0.1, 0.03-0.15, 0.03-0.2, 0.03-0.25, 0.03-0.3, 0.04-0.098, 0.04-0.1, 0.04-0.15, 0.04-0.2, 0.04- 0.25, and 0.04-0.3. In one embodiment, the at least one compound comprising at least one (meth) acrylate group constitutes at least 60 wt% of the total polymer content of the coating composition. The total weight of all polymers in the coating composition is used to calculate the ratio. The weight of all compounds comprising at least one (meth) acrylate group is divided with the weight of all polymers in the composition. In one embodiment, the at least one compound comprising at least one thiol group comprises at least two thiol groups. In one embodiment, the at least one compound comprising at least one thiol group comprises at least four thiol groups. In one embodiment, the composition comprises at least one surfactant .

In one embodiment, the composition has a pH equal to or below 7. In another embodiment, the composition has a pH equal to or below 6. In one embodiment, the composition has a pH in the interval 3-5. The pH below 7, i.e, a moderately acidic pH has the advantage of avoiding and supressing a spontaneous reaction of the system so that an increased shelf life is achieved. The shelf life is the time during which the coating composition can be stored before use. It is an advantage that a shelf life of the uncured coating composition can be made sufficiently long so that it is easy to handle the coating composition in an industrial scale. In one embodiment, the shelf life is about 12 months, in another embodiment the shelf life is about 6 months, in yet another embodiment the shelf life is about 3 months.

In one embodiment, the coating composition comprises at least one matting agent. The present coating composition is particularly suited for use with matting agents. In the present composition the shrinkage during hardening occurs to a large extent in the liquid phase compared to other acrylate based compositions. This has the effect that a matting agent with particles give a rough surface as intended also after hardening. For many other acrylate based coatings a major part of the shrinkage occurs in dry or semi-dry state so that the particles of the matting agent do not create a rough surface as intended. The method comprises the steps of a) providing a substrate, b) applying a coating composition to at least a part of the substrate, said coating composition comprising at least one compound comprising at least one (meth) acrylate group and said coating composition comprising at least one compound comprising at least one thiol group, wherein the ratio between the total number of thiol groups in the composition and the total number of

(meth) acrylate groups in the composition is in the interval 0.01-0,3, said coating composition comprises at least one compound adapted to initiate a polymerization reaction between the at least one compound comprising at least one

(meth) acrylate group and the at least one compound comprising at least one thiol group, and c) initiating a polymerization reaction in at least a part of the applied primer coating composition. It is understood that the at least one compound comprising at least one (meth) acrylate group and the at least one compound comprising at least one thiol group both are polymerizable, i.e. that they after initiation with an initiator can react and form a polymer. In one embodiment, at least one further coating is applied after step c) . In this embodiment the coating is a primer coating since there is at least one further coating on top of it. Such embodiments among others are illustrated in Fig. 4. In one embodiment, at least one selected from the group consisting of an acrylate based coating, an epoxy based coating and a dispersion is applied as the at least one further coating. In another embodiment a metal coating and/or an inorganic coating and/or biological coating is applied as the at least one further coating. In one embodiment, the at least one further coating comprises molecules of which examples include but are not limited to proteins, antibodies, nucleic acids and other biological molecules making the surface suitable for analysis, purification or handling of various molecules. In one embodiment, a biological coating is applied as the at least one further coating. The biological coating comprises at least one selected from the group consisting of a protein, a nucleic acid. Proteins include but are not limited to antibodies. Nucleic acids include but are not limited to DMA and RNA. In one embodiment, a metal coating is applied as the at least one further coating and thus the invention encompasses metallization of an object. In one embodiment, an inorganic coating is applied as the at least one further coating. Inorganic coating encompasses metal coating but includes further coatings including but not limited to a coating of ceramic or glass. It is conceived that the coating also can be used as the only coating.

In one embodiment, the coating has an embossed structure. In one embodiment, the embossed structure has features ranging from 10 nm to 1 pm. In another embodiment the embossed structure has features with aspect ratio above 1 : 1 . Embossed structures are illustrated in Fig. 4. In the embodiments in Fig. 4 the embossed coating has been applied on a substrate A. The coating can be applied on the substrate A before or after contacting with the master surface. It is preferred that the glass transition temperature is adapted to the intended use. As an example for a flooring application, the glass transition temperature for the hardened coating when used as a top coat should be at least 50 °C, preferably at least 60°C, more preferably at least

70 °C . In one embodiment, the coating composition is applied on a polymeric substrate. In one embodiment, the coating

composition is applied on a polymeric substrate comprising PVC (polyvinylchloride). In one embodiment, the coating is applied on a polymeric substrate comprising PET (Polyethylene terephthalate ) ,

In one embodiment, the coating composition is applied with a thickness in the range 0. l-100pm, the thickness being measured directly after application of the coating

composition. In another embodiment the coating composition is applied with a thickness in the range 0.5-lOOpm. In another embodiment the coating composition is applied with a thickness in the range 3--30pm. In another embodiment the coating composition is applied with a thickness in the range 0.1-5 pm. In yet another embodiment the coating composition is applied with a thickness of 5-15pm. The thicknesses of the coating apply both when the coating is the uppermost layer and when a further different layer is applied on the coating, i.e, when the coating is a primer. It should be noted that the change in coating thickness in general is very small during the hardening, i.e. when a polymerization reaction in at least a part of the applied primer coating composition is initiated. Thus, the thickness after application of the composition is generally essentially the same as after the complete curing of the coating. In one embodiment, the coating is embossed by contacting it with a master surface. In one embodiment, the pattern has a height measured perpendicular to the surface in the interval from 10 nm to 5 pm. In one embodiment, the pattern has a height measured perpendicular to the surface in the interval from 5 pm to 100 pm. In one embodiment, the pattern is a structure wherein the elements have an aspect ratio in the interval 0.9:1 to 1 . 1 : 1 . In one embodiment, the pattern is a structure wherein the elements have an aspect ratio above 1 : 1 . It is an advantage of the method and material that a patterned coating can be manufactured where the aspect ratio of the structural elements is higher than 1:1.

In one embodiment, the coating is removed from the substrate after step c) , i.e. after the curing. This is a way to manufacture a film. Often at least one further layer is added to the coating before removing it from the substrate. This provides a way to manufacture an object such as a film with a pattern. The coating is applied on a master with a pattern and after curing the coating can be removed and is then patterned according to its contact with the master surface. Often the coating according to the invention is supplemented with at least one further layer before it is removed from the master surface.

In one embodiment, a patterned structure according to the invention is subjected to an impulse of shear when the patterned master is removed from it after curing. In one embodiment, the size of the pattern is in the order of magnitude of nanometers. In one embodiment, it is a nickel- master. The invention improves the probability that the patterned coating is not damaged when it is separated from the master pattern against which it is formed during curing. It is known that such damages depend partly on surface energy and partly on mechanical properties of the coating. The invention improves the mechanical properties of the coating and thereby reduces the risk of damage to the patterned material .

In one embodiment, the polymerization reaction is initiated partially at least once in at least a part of the applied primer coating composition so that the viscosity of the coating composition is increased, and wherein the

polymerization reaction subsequently is initiated again in at least a part of the applied primer coating composition so that the coating becomes fully cured. This method improves the handling in many cases since the viscosity of an applied coating can be increased without fully hardening the coating. The coating is then fully hardened/cured later. In order to obtain such a gelling or incomplete curing, the coating is In one embodiment, irradiated with a lower energy of actinic radiation and/or during a shorter period of time.

In general, the coating is fully cured after completion of the process according to the invention.

In one embodiment, the coating is fully cured after

application of a further coating.

There is provided a coated object at least partially coated with a coating composition as described above and optionally further coatings .

There is provided use of a coating composition as described above for improving the resistance towards shear-impact wear. Shear impact implies a force in the plane of the coating and occurs in different applications. In an application the coating composition is used so that it is applied to a surface of an object and then cured. It can be either a top coat or a primer with another coating on top. The coating has such mechanical properties and such strength that it can withstand the shear impact better than other coatings ,

Shear-impact wear is a problem for instance within flooring applications . It can occur for instance when heavy furniture are moved across the floor or from footsteps. Furniture often have pads which are softer than the surface of the floor, but may nevertheless cause wear on the floor. Such wear caused by a softer object on a harder surface is typically shear impact wear. Such shear impact may result in wear of the coating and the present coating can tolerate more such shear impact without being damaged.

There is provided a method for improving the resistance towards shear-impact wear comprising applying a coating composition as described above on at least a part of the surface of an object. The coating is applied to the surface of an object and then cured. Then the coated surface is able to withstand shear-impact better.

In one embodiment, the method comprises the step of applying a further coating on the surface. Then the present coating is a primer under top-coating.

In one embodiment, the coating composition is applied to an object and the resistance towards shear-impact wear is improved for the object. The coating can tolerate more shear- impact than other coatings before any damage and wear is imparted to the coating. Thus, the resistance towards wear resulting from shear-impact is improved.

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

Chemicals used throughout different examples:

Karenz MT PEI { Pentaerytritoltetrakis ( 3-merkapto-butanol ) ) EW=136.2

PEIMP ( Pentaerythritol tetrakis (3-mercaptopropionate) )

RTMΆ (Pentaerythritol tetrakis (2-mercaptoacetate) )

IATΆTO (1, 3, 5-Triallyl-l , 3_» 5-triazine-2 , 4 , 6 ( 1H, 3H, 5H) -trione)

GPTA (Glycerol propoxylate (1P0/0H) triacrylate) EW=142.7 Sartomer SR 9051 ( 2-methyl-2-propenoic acid phosphionobis

(oxy-2, 1-ethanediyl ) ester 30-60% and propylidyntrimethanol , ethoxylated, esters of acrylic acid (<6,5 mol EO) 30-60% , from Sartomer ) EW approx . 300

BYK 361 ( Polyacrylate based wetting agent, liquid 100 % solid content, from Altana)

Omnirad 481 ( 1-Hydroxycyclohexyl phenyl ketone, from IGM resins )

TC 1 (a commercial low gloss 100% solids top coat )

TC 2 (a commercial low gloss 100% solids top coat ) Irgacure 819 is an UV-initiator from IGM Resins Dynasylan MTMO is a mercapto silane from Evonik

Example 1 , High shear-impact wear test ,

PVC floor coverings; improving the coating system^'s

resistance to high friction shear-impact wear, using a thiol additive.

High shear-impact wear test method

A solid plastic wheel with 19.5 cm diameter and 4.5 cm thickness and slightly rounded wear surface was mounted on an axle and fitted in an Arboga stationary drill machine. The wheel was rotated at 205 rpm. The coated sample was pressed towards the wear surface of the spinning wheel for 1 second using approximately 50 N force. The plastic wheel was softer than the coated surface in that it was not able to scratch the surface. The coated sample to be tested had a surface which was harder compared to the object making the shear impact, i.e. the solid plastic wheel. This was also evidenced because the plastic wheel left a layer of plastic material on the surface to be tested. This procedure subjects the coating to a shear impact where the direction of the force is applied essentially in the plane of the coating.

Each tested panels were tested 3-4 times and each tested system was represented by three identically prepared panels. The test was performed and analyzed in a blind manner. The analysis was done using ImageJ software and expressed as the area of the mark resulting from the high shear-impact wear.

Materials used

PVC 17003, a standard UV curable acrylate primer with a thiol additive, see formulation below. Standard primer, a UV curable primer for plastic materials. Sealer, a tough wear resistant UV curable industrial coating. Non-coated plasticized PVC material.

Panel preparation

The layer thicknesses are defined as the nominal thickness given by wire applicators.

PVC17003 was, if applicable, applied using 6 or 12 pm applicators. The coating was gelled using a UV dose of 150 mJ/cm². Standard primer was applied using a 6 pm applicator. The coating was gelled using a Hg UV lamp with a dose of 150 mJ/cm².

The Sealer was applied using a 6 pm applicator. The coating was fully cured using a Hg UV lamp with a dose of 1500 kJ/cm².

Results

Series 1

Series 2

Test on further materials

To test if the improvement of coating systems performance is valid in general, three more substrates were tested: · Tarkett Optima, a homogenous PVC carpet

• Forshaga Smaragd, a homogenous PVC carpet

• Black nitrile butadiene rubber sheet (NBR)

Both PVC carpets are already coated on the top side, in this experiment the down side was used were the surface consist of the bulk PVC material.

The coatings system was applied in the same way as in the above experiment, but only samples with 12 pm PVC 17003 and controls with no PVC17003 were made.

Each result is the average of 3 tests on 3 panels, so an average of 9 values.

Results

Conclusion

The result of the high shear-impact wear test is improved by using a primer with the thiol additive. The result is further improved if the layer thickness of PVC17003 is increased up to 12pm.

The effect has also been shown on several commercial PVC flooring materials and a vulcanized rubber.

PVC17003, formulation

Example 2 , Bending of coated surfaces due to curing shrinkage of coatings .

Substrate: Tarkett LVT , uncoated, white

Coatings: Commercial top coat (TC 1), modified with

increasing levels of PTMA.

The coatings were applied with a 6 mih wire applicator . The samples were weighed before and after coating to establish the amount of coating in g/m².

Curing : Two passes under a UV lamp with the doses 700 mJ/m² and 5750 mJ/cm² respectively .

Bending was measured at the centre of each sample by using a pm dial . The sample was resting on a flat surface with the convex side upward. The dial was read first when the tip lightly touched the surface of the sample and when the sample was firmly flattened to the surface . The difference was recorded as bending . The dimension of the samples were 5x7 , 5 cm.

In Fig 1, the bending is presented as a ratio between the bending in pm and the coating thickness in g/m². Example 3 , Linear scuff mark test.

Method

A 85 Shore A hard rubber heel ( 7x17 mm surface ) was pulled quickly back and forth over the substrate in an apparatus which ensures the heel moves in the same straight line during the test . The rubber heel was softer than the surface in that the material of the rubber heel was not able to scratch the surface . The rubber heel also left a trace of material on the surface to be tested. The distance between end points were 12.5 cm and each pass back and forth took about one second. The weight on the rubber heel was 11.5 kg.

The samples were evaluated after the rubber residues were removed, first gently mechanically and then with an isopropyl alcohol wipe. The scale used was:

0: No damage other than discolouration (the discolouration is due to material from the softer object moved over the surface) ; 1: Slight damages on a few spots;

2: Small but more continuous damages along the friction line;

3: a larger surface, around 10-30% is damaged;

4: Larger and deeper wounds, 30-50 % of the surface;

5: Deep wounds and damages over 50 % of the surface. For the single layer system 7.5 and 15 back and forth pulls were used. For the two-layer system 15 and 20 back and forth pulls were used.

Sample preparation

Unilin LVT was laquered with OPT001 (see formulation below) . A and B component is formulated so the thiol content can be varied without changing the initiator or wetting agent concentration. The thiol content was varied, 0, 2, 5, 10, 20 and 30wt% . 6 pm wire applicator was used. 4 samples were used for each concentration. The samples were gelled. The 0 wt% sample was oxygen inhibited also at a fairly large UV dose. The UV-dose was lowered with increasing thiol content in order to get a gelled but not fully cured material.

Half of the samples were coated with the top coat TC 2, 5.3 g/m². The samples were cured, two passes with a dose of 5750 mJ/cm²

Formulation

Stochiometry for different thiol content,

Results

The results are shown in Figures 2 and 3. Fig 2 shows the single layer system and Fig 3 shows the two layer system OPTOOl (with different SH content) and TC 2. Conclusion

Depending on the design of the system and which property is more important, there is an optimum in thiol content between 2 and 20 wt% , which corresponds to a stoichiometric ratio between thiol groups and (meth) acrylate groups of 0,018 to 0.22. Levels between 5 and 10 wt% corresponding to a stoichiometric ratio of 0.46 to 0.98 seem particularly useful, at least for certain applications.

Claims

1. A method for improving the resistance towards shear- impact wear comprising applying a coating composition, said coating composition comprising at least one compound comprising at least one (meth) acrylate group and said coating composition comprising at least one compound comprising at least one thiol group, wherein the ratio between the total number of thiol groups in the composition and the total number of (meth) acrylate groups in the composition is in the interval 0,01-0.3, said coating composition comprises at least one compound adapted to initiate a polymerization reaction between the at least one compound comprising at least one (meth) acrylate group and the at least one compound comprising at least one thiol group.

2. The method according to claim 1, wherein the ratio between the total number of thiol groups in the composition and the total number of (meth) acrylate groups in the composition is in the interval 0.01-0.25.

3. The method according to claim 1, wherein the ratio between the total number of thiol groups in the composition and the total number of (meth) acrylate groups in the composition is in the interval 0.04-0.1.

4. The method according to any one of claims 1-3, wherein the at least one compound comprising at least one (meth) acrylate group constitutes at least 60 wt% of the total polymer content of the coating composition.

5. The method according to any one of claims 1-4, wherein the at least one compound comprising at least one thiol group comprises at least two thiol groups.

6. The method according to any one of claims 1-4 , wherein the at least one compound comprising at least one thiol group comprises at least four thiol groups,

7, The method according to any one of claims 1-6, wherein the composition comprises at least one surfactant,

8. The method according to any one of claims 1-6, wherein the composition has a pH equal to or below 7.

9, The method according to any one of claims 1-6, wherein the composition has a pH in the interval 3-5.

10. The method according to any one of claims 1-9, wherein the coating composition comprises at least one matting agent.

11. The method according to any one of claims 1-10, wherein the method comprises the steps of a) providing a substrate, b) applying the coating composition to at least a part of the substrate, and c) initiating a polymerization reaction in at least a part of the applied coating composition.

12. The method according to any one of claims 1-11, wherein the substrate is flexible.

13. The method of coating a substrate according to any one of claims 1-11, wherein at least one further coating is applied after step c) .

14. The method according to any one of claims 1-13, wherein at least one selected from the group consisting of an acrylate based coating, an epoxy based coating and a dispersion is applied as the at least one further coating.

15. The method according to any one of claims 1-13, wherein a metal is applied as the at least one further coating.

16. The method according to any one of claim 1-13, wherein an inorganic coating is applied as the at least one further coating.

17. The method according to any one of claims 1-13, wherein a biological coating is applied as the at least one further coating.

18. The method according to any one of claims 1-17, wherein the coating composition is applied on a polymeric substrate .

19. The method according to any one of claims 1-18, wherein the coating composition is applied on a polymeric substrate comprising PVC (polyvinylchloride) .

20. The method according to any one of claims 1-19, wherein the coating composition is applied with a thickness in the range 0. l-100pm, the thickness being measured directly after application of the coating composition.

21. The method according to any one of claims 1-20, wherein the coating is embossed by contacting it with a master surface.

22. The method according to any one of claims 1-21, wherein the coating is removed from the substrate after step c) .

23, The method according to any one of claims 1-22 , wherein the polymerization reaction is initiated partially at least once in at least a part of the applied primer coating composition so that the viscosity of the coating composition is increased, and wherein the polymerization reaction subsequently is initiated again in at least a part of the applied primer coating composition so that the coating becomes fully cured.

24. A coated object at least partially coated according to any one of claims 1-23.