GB2605766A

GB2605766A - Composition

Info

Publication number: GB2605766A
Application number: GB2104499.5A
Authority: GB
Inventors: Shaw Dylan
Original assignee: Alphabond Tech Ltd
Current assignee: Alphabond Tech Ltd
Priority date: 2021-03-30
Filing date: 2021-03-30
Publication date: 2022-10-19
Also published as: GB202104499D0

Abstract

A composition comprises at least one additive contained within one or more waxes. Typically, the additive is an antioxidant, compatibiliser, pigment, fluorescent agent, adhesion promoter, surface tension modifier, wetting agent, filler, viscosity modifier, resin, tackifier, or UV stabiliser. The composition may comprise waxes having different melting points. The wax(es) may be natural or synthetic and may be paraffin wax, microcrystalline wax, Fischer Tropsch wax, polyethylene wax, beeswax, castor wax, carnauba wax, soy-based wax, rapeseed wax, palm wax, stearic acid vegetable wax, coconut wax, candelilla wax, sunflower wax, or rice bran wax. In a preferred embodiment, the composition is a hot melt adhesive comprising ethylene-vinyl acetate copolymer, hindered phenolic antioxidant powder, and Fischer Tropsch wax. A method of manufacturing the composition is also disclosed. In another aspect, a method of gradually releasing at least one additive into a medium at elevated temperature comprises containing the additive(s) within one or more waxes.

Description

Composition The present invention relates to a composition, which can be used in the manufacture of a product, such as an adhesive composition, and particularly a hot melt adhesive, to allow for gradual release of an additive component, such as an antioxidant, which can reduce degradation of the product during production.

Products which are manufactured at elevated temperatures, such as adhesives, encounter issues related to the degradation of the product during production due to the effect of the temperatures on the ingredients of the product.

One such product class is adhesives. Adhesives, such as hot melt adhesives, are well known for their uses in many commercial and industrial applications, such as woodworking, packaging, labelling, the bonding of laminates and personal hygiene products. A hot melt adhesive is an adhesive which is solid at room temperature and melts with healing. In use, hot melt adhesives are heated for conversion into a liquid state and applied to a substrate in order that it may adhere to another substrate. The adhesive then cools, causing it to create an adhesive bond, securing the surfaces of the substrates together. Hot melt adhesives are mostly formulated as a physical blend of raw materials like polymers, resins, waxes, and additives. There are multiple well-known methods to create ready to use hot melt adhesives. All techniques to provide homogenization of raw materials at elevated temperatures are carried out in the range of 80-220°C, and with significant shear. One of the most popular methods is blending raw materials in vessels over several hours with high shear mixers.

Such adhesives contain additive components, such as antioxidants (such as those available under the trade names Irganox 1010, Irgafos 168, and Tinuvin 770 from BASF), compatibilizers, pigments, fluorescent agents, adhesion promoters, surface tension modifiers, wetting agents, fillers, viscosity modifiers, resin/tackifiers and UV stabilisers, in small percentages to provide the desired physical and aesthetic properties of the product, and also to protect and slow down the degradation of the adhesive and the natural oxidation process. The heat stability of hot-melt adhesives can he assessed using ASTM D4499; and the thermal oxidation of a mixture applied as a hot-melt adhesive is described by Jozef et al; Polymer Testing; Vol 85; May 2020; 106422.

Taking antioxidants as an example additive, these are typically grouped into primary and secondary antioxidants, and function hy scavenging free radicals where double bonds break down. Primary antioxidants are chain-breaking antioxidants which are involved in the prevention of oxidant formation, and act by suppressing the formation of free radicals by reacting rapidly with them, while secondary antioxidants retard oxidation by preventing the proliferation of alkoxy and hydroxyl radicals by decomposing hydroperoxides to yield nonreactive products. Primary and secondary antioxidants are typically used in a synergistic combination with each other. Typically, in conventional manufacturing processes, antioxidants are added in a free powder form to the mixing vessel during manufacturing of the adhesive and are incorporated into the mix in this form.

The degradation of the adhesive starts during heating whilst manufacturing/blending the hot melt raw materials and continues when the end users re-heat the hot melt to apply it at the point of application. The adhesive can sit in hot melt glue tanks for long periods at high temperatures, and the presence of the addition of additives such as antioxidants and other components is there to slow down the process of degradation/charring/oxidation as much as possible.

However, the disadvantages of powder-based additives, such as antioxidants, are that they agglomerate easily, are difficult to add to the mix without spilling, and they do not mix very homogeneously, and can lead to patches within the mixture where it is concentrated and other areas where it is void of any of the given additive.

This means that there is often a large variation in viscosity of a product such as an adhesive between the middle of a mixing vessel and the bottom of the mixing vessel, which results in unsatisfactory variations in product consistency and quality. Additionally, some of the additive is also consumed or degraded during the manufacturing process, where high temperatures are reached. Powder-based additives are also more difficult to handle for operators because they can be easily inhaled as airborne particulates in a powder form -which is clearly not desirable from a health and safety perspective -and some can be unpleasant and hazardous chemicals to handle.

It would therefore be desirable to provide a way of avoiding these known disadvantages.

Therefore, according to the present invention there is provided a composition comprising one or more additive components contained within one or more wax materials.

Within the present invention, the one or more additive components may be selected from, but not limited to, an antioxidant, compatihilizer, pigment, fluorescent agent, adhesion promoter, surface tension modifier, wetting agent, filler, a viscosity modifier, a resin/tackifier and/or a UV stabiliser. One or more additive components may be used in the composition, and one or more of each type of additive component.

According to one embodiment of the present invention, the additive component comprises one or more antioxidants.

When the additive component comprises an antioxidant, a blend of two or more antioxidants may be used. For example, the additive component may comprise both a primary antioxidant and a secondary antioxidant, which become effective at different points in time to provide long term stability of the adhesive composition. Any organic compound with one or more radical acceptor groups and spatial hindrance, including various end groups designed for specific chemical environment could be used. Examples of antioxidants which may be used include, hut are not limited to: * Sterically hindered Phenols o lrganox 1010: Tetrakisimethylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] methane (primary antioxidant) * Phosphite Hydroxylamines a Irgafors 168: Tris(2,4-di-tert-butylphenyl) phosphite secondary antioxidant * Thiosynergist (+Phenols) o Irganox 800: Dilauryl thiodipropionate secondary antioxidant * HALS -Hindered amine light stabilizers o Tinuvin 770: Bis(2,2,6,6-tetramethy1-4-piperidinyl) scbacate (HALS) The composition may comprise from about 0.01 to about 99 wt% of the one or more additive components, typically from about 0.05 to about 75 wt%, more typically from about 0.10 to about 60 wt%, and still more typically from about 1 to about 50 wt%. Similarly, the composition may comprise from about 0.01 to about 99 wt% of the wax materials, typically from about 0.05 to about 75 wt% more typically from about 0.10 to about 60 wt%, and still more typically from about Ito about 50 wt% of the one or more wax materials.

By pre-blending the one or more additive components in one or more wax materials, it is possible to create a pellet which is easy to handle and mixes very homogeneously in the product manufacturing processes, such as an adhesive manufacturing process, ensuring protection of die mix throughout. This is very important, because any areas in a mixing vessel where additive component is essentially absent are potential spots where the raw materials will quickly degrade or oxidise. For example, the delivery of one or more antioxidant materials, as a lone antioxidant or as a blend of two or more antioxidants, when introduced into the manufacturing process, in pellet instead of traditional powder format optimises achieving the homogeneous product in this way. Additionally, the pellets are easier to handle for operators than a powder, and the wax provides some protection from skin contact with the additive component. The pellets may be of any suitable shape or size as desired.

The one or more additive components may be enclosed within one or more wax materials, or may be dispersed within the one or more wax materials.

The wax material in the composition allows the additive component to be released gradually during the manufacturing process, as the wax material is melted by the temperatures employed in the process.

The wax material may contain one or more different waxes. It is envisaged within the present invention that the wax material may contain more than one wax material, each wax material having a different melting point. This permits the wax material to be melted in a gradual and controlled manner, by controlling the temperatures employed in the product manufacturing process, melting the wax with the lowest melting point first, and so on. This also prevents the additive from being consumed during production and allows for full homogeneity of the mixture for the maximum thermal protection.

When more than one different wax is employed, different additive components may be contained individually within the different waxes. This enables them to be released sequentially when desired in a controlled manner with the increasing process 10 temperature.

This can be achieved by manufacturing the composition of the invention in such a way that different waxes containing the additive components (which may be the same or different) may be incorporated separately and individually within the composition of the invention.

This can also be achieved by manufacturing the composition of the invention in such a way that the different waxes may be blended together prior to enclosing one or more additive components therein.

Alternatively, the composition of the invention may be manufactured in a manner so the lower melting point wax is located outermost on the composition, further from the additive component and waxes with higher melting points are arranged within that, in order of their respective melting points. The wax with the highest melting point is located innermost on the product, nearest to the additive component.

The wax material used in the present invention may comprise a natural wax or a synthetic wax. The wax material may be selected from a petroleum derived wax such as paraffin wax, a microcrystalline wax, a Fischer-Tropsch wax (i.e. a synthetic wax produced from natural gas and air using the Fischer-Tropsch process), a polyolefin wax such as a polyethylene wax or a wax from natural sources, such as beeswax, a castor wax, a carnauba wax, soy based wax, rapeseed wax, palm wax, stearic acid vegetable wax coconut wax, candelilla wax, sunflower wax, rice bran wax, or a combination thereof.

Examples of the wax which may he used in the present invention include, hut are not limited to, a paraffin wax with a melting point between about 50-70°C, a micro crystalline wax with a melting point between about 60-90°C and a FischerTropsch wax with a melting point between about 50-130°C. In one embodiment of the invention, the wax may form a wax-based emulsion.

Mixtures of waxes within the present invention include two or more wax materials with different melting points. For example, two or more wax materials which have melting points in the ranges of 60-75°C. 75-100°C. and 100-130°C. Enclosed within this blend of wax materials are one or more additive components which gives the properties desired. This creates a controlled release of the additive components as the waxes melt. The purpose of the mixture is to create a slow release of the additive components during the manufacturing process to prevent them from being consumed during production and allow for full homogeneity of the mixture. Through the gradual release, the present invention also allows for a much lower degree of variation in viscosity of a composition, such as an adhesive between the middle of a mixing vessel and the bottom of the mixing vessel during the product manufacturing process, which optimises product consistency and quality.

In one embodiment of the invention, the composition may be used in the manufacture of an adhesive composition, such as a hot melt adhesive or a hot melt pressure sensitive adhesive (I-IM-PSA). There is therefore provided a method of manufacturing an adhesive composition comprising one or more additive components contained within one or more wax materials during manufacture of the adhesive composition.

By way of an example, for each hot melt adhesive formulation, the required raw materials are weighed out and added to the mixing vessel (e.g. a Kaiser mixer). A blend of the wax material and the additive components is formed by melting and mixing the wax(es) and additive component(s) in the mixing vessel at a temperature between 80-130°C. A jacketed heating system on the mixing vessel can be used to control the temperature of the mixture. The mixing temperature is determined by the melting points of the wax(es) and additive component(s).

The mixture is then melted at the selected temperature with a rotating mixing Made until a homogenous mixture with no undissolved raw materials is achieved. The blending temperature depends on the raw materials used, and the total mixing time is typically between 1.5-4 hours, depending on batch size. Also, a low molecular weight polymer will be mixed at a lower temperature than a high molecular weight polymer.

Once a homogenous mixture is achieved, the hot-melt adhesive gets transferred to the pastillation belt whereby the blend of wax(es) and additive component(s) is extruded through small nozzles into the shape of small prills or pastilles and then transferred onto a cooling belt. Once the pastilles/prills have been cooled, they are packed ready for distribution and use in the manufacturing of hot-melt adhesives.

The blending temperature is typically lower for the wax/ additive component(s) compared to that used in the preparation of hot-melt adhesives due to the lower melt point Mixing time is also shorter as there are fewer ingredients and no polymers or high melt point materials utilised.

According to a further aspect of the invention, there is provided a method of manufacturing a composition comprising one or more additive components contained within one or more wax materials, the method comprising combining the one or more 10 additive components with the one or more wax materials.

The method may involve manufacturing the composition of the invention in such a way that different waxes containing the additive components (which may be the same or different) may be incorporated separately and individually within the composition of the invention.

The method may involve manufacturing the composition of the invention in such a way that the different waxes may be blended together prior to enclosing one or more additive components therein.

Alternatively, the method may involve manufacturing the composition of the invention in a manner so the lower melting point wax is located outermost on the composition, further from the additive component and waxes with higher melting points are arranged within that, in order of their respective melting points. The wax with the highest melting point is located innermost on the product, nearest to the additive component.

The present invention also provides a method of providing a gradual release of one or more additive components into a medium at elevated temperature, comprising containing the one or more additive components within one or more wax materials.

The invention will now be described further by way of example with reference to the following examples and Figure which are intended to be illustrative only and in no way limiting upon the scope of the invention.

Figure 1 shows a representation of an additive in powder form immediately after it is added to an adhesive material, and during the mixing phase; and also an additive captured within wax immediately after it is added to an adhesive material, 10 and during the mixing phase.

More specifically, Figure 1 shows that when Irganox 1010 -an antioxidant -is added in powder form to an adhesive material and mixed ('Blend A'), it is randomly and inconsistently distributed throughout the adhesive material between the middle and bottom of the mixing vessel. This provides for an undesirable large variation in viscosity of the adhesive material between the middle and bottom of the mixing vessel, which results in unsatisfactory variations in product consistency and quality.

In contrast, when the Trganox 1010 is added within wax to an adhesive material and mixed ('Blend B'), the wax is more slowly released during mixing or agitation to give a more even and consistent distribution throughout the adhesive material, controlling the rate it is consumed during the heating/mixing process to ensure some of the antioxidant remains to protect. the in subsequent heating. This enables a more consistent distribution of viscosity within the mixing vessel between the middle and bottom of the mixing vessel. This provides for a much lower variation in viscosity of the adhesive material between the middle and bottom of the mixing vessel, which results in improved product consistency am! quality.

EXAMPLES

To investigate the_change in viscosity over a period of 7 days for different adhesives made using the present invention and using powder, a comparison was made between three adhesive samples.

The hot-melt adhesives samples are illustrated in Table 1 below and the results are shown in Table 2 below.

Table 1

Adhesive Antioxidant Wax EVA Blend lrganox 1010 Fischer Tropsch Wax Weight Weight Weight Adhesive Blend A 199.5g 0.5g Zero Adhesive Blend B 199g 0.5g 0.5g Control 200g Zero Zero Adhesive Blend A (comparative): EVA based Adhesive containing 0.25% (wt/wt) of hindered phenolic antioxidant lrganox 1010 in a powder form; Adhesive Blend B: EVA based Adhesive blend containing 0.50% (wt/wt) of antioxidant and wax, split equally between the hindered phenolic antioxidant lrganox 1010 and the Fisher-Tropsch wax, the antioxidant captured within the wax material; and Control (comparative): EVA based adhesive with no additional antioxidant added.

Method Sample adhesive blends A, B and C were prepared using the antioxidants described above. In blend B antioxidant and wax had been introduced as a previously melted and homogenized composition in pellet format in a shape suitable for a hot-melt adhesive. Each raw material was weighed out into a glass jar. Once all the components had been added, the adhesive sample Mends were placed in an oven at 160°C to melt. After 1 hour at 160°C, the samples were hand stirred using the same number of stirs with a glass rod and left in the oven for a further 30 minutes to settle.

When the sample preparation was complete, a sample was taken for the initial viscosity measurement from each sample blend.

The 3 sample adhesive blends were then placed back in the oven at 160°C for 7 days for the thermal stability test to take place.

After 7 days, the hot-melt adhesive sample blends were taken out of the oven and a sample of each blend was taken for the viscosity measurement after thermal ageing and compared with the initial viscosity data The samples were kept still for the duration of the test period, to avoid any potentially misleading results due to stratification. Samples to check the viscosity data were collected from the middle of glass jar and from the bottom. This data is given in Table 2 below.

Table 2

Adhesive Blend A Adhesive Blend B Control Initial Viscosity 2075 cps 2060 cps 2113 cps Viscosity 7 days -Middle 2675 cps 2650 cps 2938 cps Viscosity 7 days -Bottom 2800 cps 2488 cps 2988 cps Increase at Bottom 34.9% 20.7% 41.4% It can be seen that Adhesive A and Adhesive B both started with similar viscosities -Adhesive A being 2075cps @ 160°C and Adhesive B as 2060cps 160°C. the viscosity of the Control sample was higher than both, at 2113cps @ 160°C.

Viscosity was measured using the Brookfield Thermocel DV2T in accordance with ASTM D 3236; no solvent was used for the viscosity measurement.

After 7 days, the viscosity of Adhesive Blend A -where the antioxidant was added in a powder form with no wax material -increased at the bottom of the mixture to 2800cps (51) 160°C. This represents a significant overall increase of 34.94%.

Similarly, the Control sample significantly increased in viscosity at the bottom of the mixture, to 2988 cps CO 160°C -an overall increase of 41.4%.

In contrast, the viscosity of Adhesive Blend B employing the composition of the invention -where the antioxidant was added as a pre-mixture blended in waxes and added as a pellet -increased at the bottom of the mixture only to 2488 cps (0.) 160°C, which represents an increase of only 20.7%.

This significantly reduced increase in viscosity for Adhesive Blend B compared with those of Adhesive Blend A and the Control shows that there is a considerably reduced amount of thermal degradation and oxidation which has taken place.

It can therefore be seen that the addition of the antioxidant is more effective when combined with one or more wax materials and added as a pellet, giving more total thermal protection.

It is of course to be understood that the present invention is not intended to be restricted to the foregoing examples which are described by way of example only.

Claims

Claims 1. A composition comprising one or more additive components contained within one or more wax materials.
2. A composition according to claim 1, wherein the additive component is selected from one or more of an antioxidant, a compatibilizer, a pigment, a fluorescent agent, an adhesion promoter, a surface tension modifier, a wetting agent, a filler, a viscosity modifier, a resin/tackifier and/or a UV stabiliser.
3 A composition according to claim 2, wherein the additive component comprises one or more antioxidants.
4. A composition according to claim 3, wherein the antioxidant comprises a primary antioxidant and a secondary antioxidant.
5. A composition according to any preceding claim, wherein the additive component is contained or dispersed within the wax material.
6. A composition according to any preceding claim, wherein the wax material comprises two or more different waxes.
7. A composition according to claim 6, wherein the two or more different waxes each have different melting points.
8 A composition according to any preceding claim, wherein the wax material comprises a natural wax and/or a synthetic wax.
9 A composition according to claim 8, wherein the wax is selected from: a petroleum derived wax such as paraffin wax, a microcrystalline wax, a Fischer Tropsch wax, a polyethylene wax or a wax from natural sources, such as beeswax, a castor wax, a carnauba wax, soy-based wax, rapeseed wax, palm wax, stearic acid vegetable wax, coconut wax, candelilla wax, sunflower wax, rice bran wax, or a combination or any two or more thereof.
10. A method of manufacturing a composition comprising one or more additive components contained within one or more wax materials according to any preceding claim, the method comprising combining the one or more additive components with the one or more wax materials.
11. A method of manufacturing an adhesive composition comprising adding a composition comprising one or more additive components contained within one or more wax materials during manufacture of the adhesive composition.
12. A method of providing a gradual release of one or more additive components into a medium at elevated temperature, comprising containing the additive components within one or more wax materials.