CZ2015902A3

CZ2015902A3 - A packaging multilayer film with antimicrobial effects and the method of its production

Info

Publication number: CZ2015902A3
Application number: CZ2015-902A
Authority: CZ
Inventors: Stanislav Vašíček; Jiří Svoboda; Tomáš Obr; Svobodová Alice Tesaříková; Dagmar Měřínská; Zdenka Pšeničková
Original assignee: Invos, Spol. S R.O.; Univerzita Tomáše Bati ve Zlíně; Synpo, A.S.
Priority date: 2015-12-15
Filing date: 2015-12-15
Publication date: 2017-02-15
Also published as: CZ306501B6

Abstract

Obalová vícevrstvá fólie s antimikrobiálními účinky a sníženou ekologickou zátěží tvořená laminátem dílčích fóliových vrstev o celkové tloušťce do 100 .mi.m, která ve své vícevrstvé struktuře obsahuje: fóliovou vrstvu (a) o tloušťce do 20 .mi.m na bázi nízkohustotního polyetylénu (LDPE) s hustotou do 900 kg/m.sup.3.n.nebo směsi nízkohustotního polyetylénu (LDPE) a lineárního polyetylénu s nízkou hustotou (LLDPE), fóliovou vrstvu (b) o tloušťce do 70 .mi.m na bázi polypropylénu (PP), koextrudované fólie (b3) polypropylén – nízkohustotní polyetylén (PP-LDPE) nebo dvojvrstvy fólie (b1) z polypropylénu (PP) a fólie (b2) z nízkohustotního polyetylénu (LDPE), s tím, že alespoň jedna z vrstev (a,b) je opatřena směrem k vnitřní straně obalu orientovaným nánosem aktivní vrstvy (c) o tloušťce minimálně 10 .mi.m na bázi laku obsahujícího alespoň jednu enkapsulovanou antimikrobiální látku přírodního, zejména rostlinného původu (dále „aktivní vrstva“) a směrem k vnější straně obalu orientovaným potiskem bariérové vrstvy (d) o tloušťce 2 až 5 .mi.m, obsahující nanočástice jílu (dále „bariérová vrstva“) a obě fóliové vrstvy (a,b) jsou spojeny prostřednictvím adhezivní mezivrstvy (e) laminačního lepidla o tloušťce 2 až 5 .mi.m.A multi-layered film with antimicrobial effects and a reduced ecological load consisting of a laminate of sub-film layers of a total thickness of up to 100 microns, comprising in its multilayer structure: a film layer (s) of thickness up to 20 microns based on low density polyethylene ( LDPE) with a density of up to 900 kg / m.sup.3 or a mixture of low density polyethylene (LDPE) and linear low density polyethylene (LLDPE), a polypropylene-based film layer (b) up to 70 µm.m PP), coextruded film (b3) polypropylene - low density polyethylene (PP-LDPE) or bilayer film (b1) of polypropylene (PP) and low density polyethylene (bDP) film (LDPE), with at least one of the layers (a) b) is provided with a coating of active layer (c) having a thickness of at least 10 microns on the inside of the container, based on a lacquer containing at least one encapsulated natural antimicrobial substance, in particular of vegetable origin (hereinafter referred to as "active layer") and towards the outer side of the packaging by printing a barrier layer (d) 2 to 5 µm thick, containing clay nanoparticles (hereinafter "barrier layer") and both foil layers (a, b) ) are bonded by means of an adhesive laminate adhesive layer (s) 2 to 5 µm thick.

Description

Packaging Multilayer Foil with Antimicrobial Effects and Method of Production thereof

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-layer packaging film having antimicrobial properties and a reduced environmental load, consisting of a laminate of film layers. Further, the invention relates to a method of making the film.

Background Art

As antimicrobial additives of polymers, respectively. antimicrobial layers of plastic films are used in various inorganic compounds, recently with particle sizes in the order of nano dimensions. For example, an LDPE-based wrapping film according to Chinese patent application CN1134343333 contains a nanolayer with an antimicrobial compound with silver ions. The subject matter of the other Chinese patent application CNJ104151831 is a packaging film with the ability to continuously release the active ingredient to inhibit the growth of microorganisms and thereby extend the shelf life of the packaged food. Antibacterial additives of ABS-based silicone polymer-based films are zinc oxide nanoparticles and nanoscale particles.

The nanocrystalline antimicrobial additive also contains food packaging films according to Korean patent KRJ 01004027 made of polyethylene, polypropylene, polystyrene, polyester, polyvinyl chloride, polyvinylidene chloride or polyethylene terephthalate. From the ecological point of view, however, organic antimicrobial substances of natural origin - essential oils - appear more promising and more effective. Essential oils are substances of plant origin and are derived from plant material, in particular by extraction and subsequent distillation with water vapor. The product of this distillation is called the essential oil. Essential oils are terpenes and terpene derivatives, but also hydrocarbons, alcohols, aldehydes, ketones, carboxylic acids and other substances. Typical properties of essential oils and essential oils are volatility and strong biological activity even when the state is changed. This property is acceptable for applications where no significant increase in temperature is expected when incorporating these substances into the final product.

The use of natural monoterpenes and oxidation products derived therefrom as antimicrobial additives for cosmetic, pharmaceutical, food products and feedstuffs is known, for example, from PCT International Patent Application Publication No. WC) of 200-101.

Patent Application US 200311-3385 · in turn addresses the application of extracts from plants of the order Leptospemum and Melaleuca in veterinary medicine, where the use of preparations based thereon can reduce antibiotic doses, eg in the treatment of mastitis.

However, there are many sectors where elevated temperatures cannot be avoided, with the uneconomical loss of volatile essential oils and essential oils. Specifically, it is also the plastics industry, where the use of essential oils and plant extracts as antimicrobial is in this respect.

“GZ additives problematic. For example, a solution according to the patent Cft. No. 303724, which relates to an antimicrobial component comprising at least one of isoprenoids, terpenes or derivatives thereof or unsaturated ethers, under volatile liquid normally mobilized on a solid sorbent carrier. The sorbent may advantageously be an organic-based substance based on polysaccharides or derivatives thereof, in particular cellulose or starch, a substance having a chemical basis in polyphenols such as lignin, a substance of organic origin based on peptides and their derivatives, a substance based on aluminosilicates (zeolites) and other materials containing silicon dioxide, or a substance of inorganic origin based on plastic fillers, in particular based on inorganic calcium salts, in particular carbonates and sulphates, carbon black or talc. In the antimicrobial components of the present invention, terpenes and other liquid liquid flavorings are immobilized on carriers to provide enhanced thermal protection against elevated temperatures, and a reduction in vapor pressure of the systems as such is expected. terpenes and other flavorings immobilized on solid supports will not evaporate under normal conditions as quickly as if they were in liquid form. The modified system then provides greater applicability of these substances, especially the use of their antimicrobial properties in a wide range of the above applications. However, it is only a partial solution that does not specifically specify the incorporation of an antimicrobial additive into the packaging film structure or the packaging film. a method of making such a film.

SUMMARY OF THE INVENTION In order to overcome this drawback, a multilayer film packaging solution with antimicrobial effects and improved recyclability according to the invention contributes. It is a multilayer film consisting of a laminate of partial film layers of a total thickness up to 100 µm. The essence of the invention is that the film in its multilayer structure comprises: a) a film layer up to 20 µm thick based on low density polyethylene (LDPE) with a density of up to 900 kg / m or a mixture of low density polyethylene (LDPE) and linear polyethylene low density (LLDPE), b) foil layer up to 70 μιη polypropylene (PP) based, coextruded polypropylene - low density polyethylene (PP-LDPE) or polypropylene (PP) and low density polyethylene (LDPE) bilayer film, c ) towards the inner side of the package, a coating of active layer at least 10 µm thick based on a varnish containing at least one encapsulated antimicrobial substance of natural, especially vegetable origin (hereinafter "active layer"); a thickness of 2 to 5 µm containing nanoparticles of clay (hereinafter "barrier layer"), e) at least one adhesive between the laminating adhesive layer 2 to 5 µm thick. In a particular embodiment, the inner side of the package may be a 5 to 20 µm permeable layer based on low density polyethylene (LDPE) with a density of up to 900 kg / m 3 or a mixture of low density polyethylene (LDPE) and linear low density polyethylene (LLDPE). The outer layer is bonded by means of an adhesive interlayer of a laminate adhesive of 2 to 5 µm multilayer structure. This, in the direction from the outside of the package to the adhesive between the layers, comprises a polypropylene film or a coextruded film of polypropylene-low-density polyethylene (PP-LDPE) having a thickness of 60 to 70 µm, printing a barrier layer of 2 to 5 µm and depositing the active layer at least 10 pm. In another embodiment, the inner side of the package forms a multilayer structure comprising a low density polyethylene based film having a density of up to 900 kg / m 3 and a thickness of up to 15 µm provided with a zonal coating of the active layer of thickness on one side of the container. at least 10 µm, while on its other side it is provided with a barrier layer of 2 to 3 µm thick. Further to this side, a polypropylene film having a thickness of up to 55 µm is formed by an adhesive intermediate layer of the laminating adhesive 2 to 3 µm, forming the outer side of the multilayer packaging film. In a further possible embodiment, the inner side of the package forms a multilayer structure which comprises a low density polyethylene film having a density of up to 900 kg / m 3 and a thickness of up to 20 µm which is coated on one side with a layer of active layer of at least a thickness of With a barrier layer of 2 to 5 µm, a polypropylene film having a thickness of up to 70 µm forming the outer side of the multilayer packaging layer is attached thereto via an adhesive intermediate layer of the laminating adhesive having a thickness of 2 to 5 µm; foil.

The antimicrobial substance of natural origin is then preferably essential oil or oil, oil, in particular essential oil, rosemary, garlic, thyme, cinnamon, sage, fennel, or good-natured, encapsulated in a micronized porous mineral filler such as zeolite or silica gel in an amount of 5%. up to 30% by weight, depending on the porosity of the particular mineral filler.

Preferably, the liquid-containing lacquer comprises 0.7 to 10.0% by weight of the encapsulated essential oil and the dry weight of the active layer is 2.0 to 20.0% by weight of the encapsulated essential oil.

The lacquer of the barrier layer preferably comprises 0.5 to 10.0% by weight of intercalated and exfoliated clay nanoparticles with a particle size of 100 to 500 nm.

The essence of the process for the production of a multilayer film according to the invention is that the individual film layers are first produced by extrusion - a film layer up to 20 µm thick based on low density polyethylene with a density of up to 900 kg / m 3 or a mixture of low density polyethylene (LDPE) and linear polyethylene with low density (LLDPE), and a polypropylene-based low density polyethylene (PP-LDPE) foil layer up to 70 µm thick. One of them is coated with a 2 to 5 µm barrier layer lacquer and an active layer with an encapsulated antimicrobial agent of natural origin with a thickness of at least 10 µm is spray-sprayed. The two film layers are then bonded by lamination through a 2 to 5 µm adhesive interlayer. In a particular embodiment of the inventive packaging multilayer film process, a 5 to 20 µm film permeable layer is first produced by extrusion based on low density polyethylene or a low density polyethylene (LDPE) mixture. and low density linear polyethylene (LLDPE) and a polypropylene or low density polyethylene (PP-LDPE) based polypropylene or coextruded polypropylene - low density polyethylene (PP-LDPE) film layer, to which a first layer of the barrier layer is applied, followed by spray painting layers. The film permeable layer and the multilayer polypropylene film layer layer with barrier and active coating are then bonded by lamination through an adhesive laminate adhesive layer. In another variant of the process for producing the multilayer packaging film according to the invention, a polypropylene film having a thickness of up to 70 µm is first produced by extrusion for an outer layer and a film thickness up to 20 µm based on low density polyethylene with a density of up to 900 kg / m 2 for the inner structure of the package. On the low-density polyethylene sheet, on the one hand - forming the inner side of the package - with the exception of the weldable regions - an active layer with a thickness of at least 10 µm is applied by spraying, and on the other hand a barrier layer having a thickness of 2-3 µm is printed. The polypropylene film of the outer layer is then bonded to the structure thus formed by lamination by means of an adhesive interlayer of the laminating adhesive. In a further variant of the process for the production of the multilayer packaging film according to the invention, a 60-70 µm film layer based on polypropylene or a co-extruded polypropylene-low-density polyethylene film (PP-LDPE1 and a foil-permeable layer of 5-20 µm on a low density polyethylene basis) is first produced by extrusion. or a blend of low density polyethylene (LDPE) and linear low density polyethylene (LLDPE) to which the active layer spray is first applied by spraying, and then the barrier layer lacquer is applied by printing, a polypropylene-based or coextruded polypropylene film layer 60 to 70 µm thick low density polyethylene (PP-LDPE) and a multilayer structure of the permeable layer with barrier and active coating are then laminated through an adhesive laminate adhesive interlayer.

EXAMPLES Example 1 In the capping film of the containers according to Fig. 1, the inner side of the package forms a permeable film layer and a low density polyethylene with a density of up to 900 kg / m 3 of a thickness of 10 µm. The multilayer structure is attached from the outside by means of an adhesive intermediate layer 3m laminating adhesive. In the direction from the outside of the package to the adhesive interlayer, it comprises a film layer b of polypropylene of 54 µm, a barrier layer of up to 3 µm thick, comprising nanoparticles of clay and a coating of active layer 30 µm thick based on a lacquer containing an encapsulated antimicrobial substance of natural origin garlic. silici. In the manufacture of the aforementioned capping film, a film layer of 10 .mu.m of low density polyethylene is first produced by extrusion and a film layer of 54 .mu.m is made of polypropylene.

which is first applied by the coating of the barrier layer and subsequently by the technology of coating the active layer with the encapsulated antimicrobial substance.

origin. In the management, the active layer lacquer is applied to the moving carrier polypropylene film provided with printing marks by the nozzles of the spraying device. The process of applying the active lacquer to the carrier film, the timing of the spraying device, and the final location of the coating on the carrier film is controlled by the position of the printing mark on the carrier film. The subsequent drying process takes place in a manner that is friendly to the active ingredients encapsulated in the active lacquer, i.e., an air flow rate of 500 to 600 m / min and a temperature of up to 40 ° C. The film permeable layer and the multilayer structure based on the polypropylene film layer with barrier and active coating are then laminated by means of an adhesive interlayer and laminating adhesive. Example 2 The lidding film of the packaging of another embodiment (according to FIG. 2) has an inner side of the package comprising a multilayer structure comprising a foil layer and a low density polyethylene having a density of up to 900 kg / m 3 and a thickness of 10 µm. with the exception of weldable areas, with a zonal coating of the active layer of a thickness of 25 µm, based on a lacquer containing thyme oil as an encapsulated antimicrobial substance of natural origin, while on the other hand it is printed with a barrier layer up to a thickness of 3 µm containing nanoparticles of clay. In addition, a film layer b of polypropylene having a thickness of 59 microns forming the outer side of the multilayer packaging film is bonded to this side by an adhesive intermediate layer 3m laminating adhesive. In the production of this capping film, a film layer or a thickness of 59 .mu.m is first produced by extrusion of polypropylene for the outer layer and the film layer and a thickness of 10 .mu.m of low density polyethylene. On the one side - forming the inner side of the package - on the one side - except for the weldable areas - the active layer is applied to the foil layer and low density polyethylene on the basis of a varnish containing at least one encapsulated antimicrobial substance of natural origin and on the other hand the barrier layer is printed on a thickness of 3 pm. The resulting film is then laminated by means of an adhesive interlayer of a 3 µm laminating adhesive to a film layer b from a polypropylene outer layer of the package. EXAMPLE 3 The capping film of FIG. 3 comprises a film layer and a low density polyethylene having a density of up to 900 kg / m < 3 > m, which is coated on one side with an active layer of 15 [mu] m on the outside of the pack. a base of lacquer containing as an encapsulated antimicrobial substance of natural origin a silica oil and further provided on it with a barrier layer up to a thickness of 3 µm containing nanoparticles of clay, wherein a film layer or thickness of about 3 µm is attached to this side by a 3 µm laminating adhesive adhesive layer 62 µm of polypropylene forming the outer side of the multilayer packaging film. In the production of this capping film, a film layer of a thickness of 62 µm is first produced by extrusion and made of polypropylene and a film layer and a thickness of 15 µm of low density polyethylene, to which technology is first applied.

lacquer of active layer en encapsulated antimicrobial substance of natural origin - by clove oil and then by printing the coating of the barrier layer d. The foil layer 62 of the polypropylene and the multilayer structure of the permeable layer with barrier and active coating is then laminated by means of an adhesive interlayer and laminating adhesive . Example 4

The structure of the lidding film of the containers (see Fig. 4) is similar to Example 1. However, the film layer b of the polypropylene layer of the outer side of the package is replaced by a foil bilayer consisting of a 49 µm polypropylene film and a low density polyethylene film b2 below it. 10 pm. Example 5

The structure of the lidding film of the containers (see Fig. 5) is similar to Example 1. However, the film layer b of the polypropylene of the outer side encapsulates here a 50/15 µm co-extruded film b3 of polypropylene-LDPE. Example 6

The structure of the capping film of the containers is identical to that of Example 1. The film layer and the low density polyethylene on the inside of the package are replaced by a film of a mixture of low density polyethylene (LDPE) and linear low density polyethylene (LLDPE) of 15 µm thickness. The web is attached from the outside by a 2 µm multilayer structure via an adhesive interlayer. In the direction from the outside of the container to the adhesive interlayer, it comprises a 65 µm polypropylene film, a barrier layer of 3 µm thick, containing a nanoparticle clay and an active layer coating of 15 µm based on a lacquer containing as an encapsulated antimicrobial natural rosemary oil. Example 7

The structure of the capping film of the containers is the same as that of Example 2. The inner side of the wrapper consists of a multilayer structure comprising a film layer and a low density polyethylene with a density of up to 900 kg / m 3 and a thickness of 15 µm. provided with a zonal coating of active layer 15 μιη on the base of varnish containing sage oil as an encapsulated antimicrobial birthing material, while on the other side it is provided with a barrier layer of up to 3 µm thickness. Further to this side, a laminated layer of 2 µm laminated adhesive is bonded to the side by means of an adhesive layer b of a 2 µm thick polypropylene forming the outer side of the multilayer packaging film.

Claims

PATENT CLAIMS

1. A multilayer film with antimicrobial effect and a reduced ecological load consisting of a laminate of sub-film layers having a total thickness of up to 100 µm, comprising in its multilayer structure: a film layer (s) having a thickness of less than 20 μιη based on low density polyethylene ( LDPE) with a density of up to 900 kg / m or a mixture of low density polyethylene (LDPE) and linear low density polyethylene (LLDPE), a foil layer (b) up to 70 µm based on polypropylene (PP), coextruded film (b3) polypropylene - low density polyethylene (PP-LDPE) or polypropylene (PP) double layer foil (b1) and low density polyethylene (LDPE) foil (b2), provided that at least one of the layers (a, b) is provided towards the inside of the coating with an oriented coating of active layer (c) of at least 10 µm thickness based on a lacquer containing at least one encapsulated natural antimicrobial agent, The plant layer (hereinafter referred to as "active layer 44") and towards the outside of the container oriented printing of the barrier layer (d) having a thickness of 2 to 5 µm, containing clay nanoparticles (hereinafter "barrier layer 44"), and both foil layers (a, b) are joined by an adhesive a laminating adhesive intermediate layer (s) 2 to 5 µm thick.

Packaging multilayer film according to Claim 1, characterized in that the inner side of the packaging comprises a permeable film layer (a) of 5 to 20 µm thickness based on low density polyethylene (LDPE) with a density of up to 900 kg / m3 or a mixture of low density polyethylene (LDPE). ) and a linear low density polyethylene (LLDPE), the outer layer of which is bonded through the adhesive laminate adhesive layer (s) to a 2 to 5 µm multilayer structure, which comprises a film layer (b) in the direction from the outside of the package to the adhesive interlayer. 60 to 70 µm thick polypropylene foil or coextruded foil polypropylene - low density polyethylene (PP-LDPE), 2 to 5 µm barrier layer (d) printing, and coating of active layer (c) at least 10 µm thick.

A multilayer film according to claim 1, characterized in that the inner side of the packaging comprises a multilayer structure comprising a film layer (a) of low density polyethylene having a density of up to 900 kg / m 3 at a thickness of up to 20 µm. - the inner side of the package - with the exception of weldable areas provided with a zonal coating of the active layer (c) o <?), a thickness of at least 10 pm, while on its other side it is provided with a barrier layer (d) of thickness 2 to 5 μηι with the addition of a laminate layer (b) of polypropylene having a thickness of up to 70 µm, forming the outer side of the multilayer packaging film, by means of an adhesive intermediate layer of a laminating adhesive of 2-5 µm.

The multilayer packaging film according to claim 1, characterized in that the inner side of the packaging comprises a multilayer structure comprising a low density polyethylene based layer (a) having a density of up to 900 kg / m 3 at a thickness of up to 20 µm. side-facing to the outside of the wrapper is provided with a layer of active layer (c) of at least 10 µm thickness and further provided with a barrier layer (d) of 2 to 5 µm on the side, furthermore by means of an adhesive interlayer (e) ) of a laminating adhesive having a thickness of 2 to 5 µm attached to a film layer (b) having a thickness of up to 70 µm of polypropylene forming the outer side of the multilayer packaging film.

Packaging multilayer film according to one of Claims 1 to 4, characterized in that the antimicrobial substance of natural origin is essential oil or oil, in particular clove, rosemary, garlic, thyme, cinnamon, sage, fennel or micronized encapsulated essential oil. a porous mineral filler such as zeolite or silica gel in an amount of from 5 to 30% by weight, depending on the porosity of the particular mineral filler.

Packaging multilayer film according to one of Claims 1 to 5, characterized in that the liquid layer of the active layer comprises 0.7 to 10.0% by weight of encapsulated essential oil and the dry matter of the active layer is 2.0 to 20.0% by weight of encapsulated essential oil.

Packaging multilayer film according to Claims 1 to 6, characterized in that the barrier layer lacquer contains 0.5 to 10.0% by weight of intercalated and exfoliated clay nanoparticles with a particle size of 100 to 500 nm.

Method for producing a multilayer film according to claim 1, characterized in that the individual film layers are first produced by extrusion - a film layer (a) of thickness up to 20 µm based on low density polyethylene with a density of up to 900 kg / m3 or a mixture of low density polyethylene ( LDPE) and linear low density polyethylene (LLDPE), and filament layer (b) with a thickness of up to 70 µm based on polypropylene or co-extruded polypropylene film-low density polyethylene (PP-LDPE), some of which are coated with a barrier coating

a layer (d) having a thickness of 2 to 5 µm and a spraying technology of the coating of the active layer (c) with a thickness of at least 10 µm, comprising at least one encapsulated antimicrobial substance of natural, in particular of plant origin, and laminating the two film layers by means of an adhesive interlayer (s) o thickness 2 to 5 μιη.

Method for producing a multilayer film according to claim 8, characterized in that a permeable film layer (a) having a thickness of 5 to 20 µm is produced by extrusion on the basis of low density polyethylene or a mixture of low density polyethylene (LDPE) and low density linear polyethylene ( LLDPE) and foil layer (b) with a thickness of 60 to 70 µm based on polypropylene or co-extruded foil polypropylene - low density polyethylene (PP-LDPE), to which first the coating of the barrier layer (d) is applied followed by technology

lacquer of the active layer (c), whereupon the film-permeable layer and the multilayered polypropylene film-based layer layer with barrier and active coating are laminated by means of an adhesive laminate adhesive layer (s).

Method for producing a multilayer film according to claim 8, characterized in that a film layer (b) of polypropylene with a thickness of up to 70 µm is first produced by extrusion for the outer layer and a film layer (a) of up to 20 µm is made of low density polyethylene with a density of up to 900 kg / m 3 for the inner structure of the package, on which the active layer (c) of at least 10 µm is applied on the one side - forming the inner side of the package - except for the weldable regions, and on the other side the printing of the barrier layer (d) 2 to 5 µm, whereupon the polypropylene film of the outer layer is bonded to the resulting structure by lamination through an adhesive laminate adhesive intermediate layer (e).

Method for producing a multilayer film according to claim 8, characterized in that a film layer (b) having a thickness of 60 to 70 µm is produced first by extrusion from polypropylene or a co-extruded film polypropylene - low density polyethylene (PP-LDPE) and a permeable film layer ( (a) 5 to 20 µm thickness of low density polyethylene or a mixture of low density polyethylene (LDPE) and linear, low density polyethylene (LLDPE) to which technology is first applied

the lacquer of the active layer (c) and then applying the lacquer of the barrier layer (d), followed by a 60-70 µm-based polypropylene or co-extruded polypropylene-low-density polyethylene (PP-LDPE) film layer and a multilayer permeable layer structure. by bonding and laminating through the adhesive interlayer (s) of the laminating adhesive.