FR3144047A1 - Multi-layer structure for creating a floor covering - Google Patents

Abstract

The invention relates to a multi-layer structure for producing a floor covering, the multi-layer structure (1) being devoid of coupling means and comprising successively: - an upper PVC wear layer (2) comprising 20 to 50 PCR plasticizer, and having a thickness of between 0.3 and 2 mm, preferably between 0.5 and 1 mm; - a first reinforcing frame (3); - a bonding layer (4) of plasticized PVC making it possible to bond the reinforcing reinforcement (3) has a backing layer (5);- said backing layer (5), which is made of compact PVC and comprising 40 to 60 PCR of plasticizer, and a loading rate greater than 130 PCR, even greater than 150 PCR, even greater than 200PCR and up to 250 PCR; - a foamed underlayer (6) in plasticized and loaded PVC; the backing layer (5) having a thickness of between 0.4 and 2 mm, and the bonding layer (4) comprising from 20 to 50 PCR of plasticizer and a loading rate of less than 5% by weight of the layer bonding (4) and having a thickness of between 0.05 and 0.5mm. Figure for abstract: Fig. 1

Description

Multi-layer structure for creating a floor covering

The present invention relates to a multilayer structure with acoustic insulation property, devoid of coupling means and presented in slabs, strips, for the production of a floor covering in semi-free installation using a tackifier or double-sided adhesive, even in glued installation, or presented in rolls for the creation of a loose-laying floor covering.

Prior art

It is known from the state of the art a multi-layer structure devoid of coupling means, presented in tiles, strips, or rolls, for the production of a floor covering with acoustic insulation properties.

This multilayer structure successively comprises, that is to say from the top towards the ground:
- an upper wear layer of plasticized PVC, having a thickness of between 0.3 and 2 mm;
- a layer of plasticized PVC backing, compact, that is to say not foamed, obtained, not by coating, but rather by calendering, pressing or extrusion, the backing layer is plasticized and with a load rate greater than 130 PCR (per hundred parts of resin), or even greater than 150 PCR;
- a foamed underlayer in plasticized and loaded PVC.

In order to facilitate installation and improve the dimensional stability of this type of floor covering, it is known that the backing layer comprises a reinforcing frame, such as a glass veil coated with a PVC plastisol gelled on its two faces and placed in contact with the wear layer.

To facilitate installation, in particular free installation, the structure must be balanced and, to do this, it is known to add fillers in the PVC backing layer or to increase its thickness to have a thickness greater than 2 mm. However, an excessive increase in the thickness of the backing layer can degrade the acoustic insulation performance of the structure. Conversely, an increase in the thickness of the foamed underlayer degrades the puncture resistance.

Furthermore, for surfaces greater than 30 m², or even greater than 50 m², the installation of this type of covering in rolls still requires the use of glue to ensure maintenance.

The resulting disadvantage is that the total thickness of the structure becomes too great, particularly if the thickness is greater than 6 mm, which results in too much weight, of the order of 6 to 10 kg/m², and therefore logistical difficulties and environmental impact issues.

Document EP3505342 describes, for its part, the implementation of a second layer reinforced with a second reinforcing frame, which makes it possible to stiffen the structure and form a so-called “bimetal” effect, contributing to the lead effect of the slab, which makes it easier to install. However, this type of structure does not allow the use of materials from recycled PVC in its composition.

Another disadvantage of the prior art is encountered when the upper wear layer is transparent, with 20 to 50 PCR of plasticizer, and a zero charge rate, or even less than 5% by weight of the upper layer.

In this situation, the low quantity of load leads, during the manufacture of the structure, to a withdrawal of the wear layer which gives rise to the phenomenon well known to those skilled in the art under the English term "curving". in French, in which the periphery of the multilayer structure rises, which creates an imbalance.

Another disadvantage of the prior art is encountered when the foamed PVC underlay has a plasticizer rate of between 20 to 60 PCR, and a charge rate of less than 130 PCR, or even less than 100 PCR.

In this situation, the difference in load rate with the backing layer leads, during the manufacture of the structure, to a shrinkage of the foamed underlay which generates the phenomenon of curvature in French, contributing to the imbalance.

One of the aims of the invention is therefore to propose a multilayer structure for the production of a floor covering, which is balanced, suitable for free installation in the case of a roll, and without coupling means, with a satisfactory rigidity to withstand the passage of heavy loads, while having an acoustic attenuation greater than 15 dB or even 19 dB according to NF EN ISO 717-May 2, 2013 and NF EN ISO 10140-July 3, 2021 and a lower sound level when walking at 65 according to NF EN 16205 August 2013 / NF EN 16205/IN1 May 2018 / NF S 31-074.

For this purpose, a multi-layer structure has been developed for the production of a floor covering devoid of coupling means and comprising successively, that is to say from the top towards the ground:
- an upper PVC wear layer comprising 20 to 50 PCR of plasticizer (PCR means per hundred parts of resin), and having a thickness of between 0.3 and 2 mm, preferably between 0.5 and 1 mm;
- a first reinforcement frame;
- a plasticized PVC bonding layer allowing the reinforcement to be bonded to a backing layer;
- said backing layer, which is made of compact PVC and comprising 40 to 60 PCR of plasticizer, and a loading rate greater than 130 PCR, or even greater than 150 PCR, or even greater than 200 PCR and up to 250 PCR;
- a foamed underlayer in plasticized and loaded PVC.

According to the invention, the backing layer has a thickness of between 0.4 and 2 mm, preferably between 0.6 and 1.5 mm, and the bonding layer comprises from 20 to 50 PCR of plasticizer and a rate of load less than 5% by weight of the bonding layer and has a thickness of between 0.05 and 0.5mm, preferably between 0.1 and 0.3mm.

The presence of the bonding layer according to the invention makes it possible to balance the structure, without requiring an increase in the thickness of the loaded PVC backing layer.

In practice, the presence of the bonding layer according to the invention, which is plasticized and which includes a low load rate, makes it possible to generate the phenomenon of reverse curvature of the wear layer, well known to man. of the profession under the English term “doming” in which the edges of the structure lower (or the center rises), creating an inverse imbalance which therefore compensates and rebalances the structure.

Given the low loading rate in the bonding layer, it has a lower surface mass than the backing layer which is loaded and therefore heavier. In other words, the invention makes it possible to rebalance the structure, with a lower weight, compared to the known solution consisting of increasing the thickness of the backing layer, while preserving the acoustic and puncture resistance performances. of the structure.

The high level of plasticizer in the backing layer increases the flexibility of the structure. The presence of the bonding layer according to the invention therefore also makes it possible to stiffen the multilayer structure with a minimum of material, with a view to facilitating installation, reducing the weight compared to the prior art, and consequently reducing the 'environmental impact.

In a particular embodiment, the upper wear layer is transparent and comprises 30 to 50 PCR of plasticizer, with a zero charge rate, or even less than 5% by weight of the upper layer, and the multilayer structure comprises a layer decoration positioned under the upper wear layer.

In a particular embodiment, the upper wear layer has a chamfer on its upper face and on at least one edge of the roller or the slab or blade, preferably on all four edges. The presence of a chamfer can lead to a reduction in the traffic resistance performance of the structure, which generates a “starter” zone for the structure to detach. This effect is limited by the characteristics of the multilayer structure according to the invention.

The decoration layer can for example be in the form of a layer of ink printed on a lower face of the wear layer, or on an upper face coated with the first reinforcement, or on an upper face of a decorative film positioned under the wear layer.

In this configuration, the low load rate in the upper plasticized PVC wear layer generates the phenomenon of “curving” or incurvation tending to unbalance the multilayer structure, compensated by the bonding layer.

According to another embodiment, the wear layer can be in the form of a layer of pressed granules, so that the wear layer itself forms the decoration. The granules can be of any desired color, as is well known from the state of the art.

The layer of pressed granules is obtained from plasticized and filled PVC. Generally speaking, the loading rate of the pressed granules is much lower than 130 PCR, preferably lower than 100 PCR or even 80 PCR so as to present good scratch resistance. The layer of pressed granules thus tends to generate a “curving” or incurvation phenomenon tending to unbalance the multilayer structure, which is compensated by the bonding layer.

Advantageously, the multilayer structure comprises a second reinforcing frame, embedded in the surface of the backing layer and also linked to a lower face of the first reinforcing frame by the bonding layer.

Alternatively, the multilayer structure comprises a second reinforcing reinforcement, embedded on the reverse side of the reverse layer, on the surface of the underlayer so as to produce a bimetal effect. This is for example directly linked to the underlay during the manufacture of the structure by coating the underlay in PVC plastisol on the second reinforcing frame then gelling.

This second frame makes it possible to improve the rigidity of the multi-layer structure, and in particular to improve the resistance test for the chair on wheels.

The bonding layer is for example a layer of plastisol, preferably a PVC plastisol. This makes it possible in particular to simplify the manufacturing process of the multilayer structure by depositing a PVC plastisol by coating on the first reinforcement or on the surface of the backing layer, then bringing the assembly formed by the wear layer into contact. , the first reinforcing reinforcement and the backing layer and to gel the plastisol so as to obtain the bonding layer and bind the whole.

Preferably, the foamed underlayer has a thickness of between 1 and 3mm, preferably between 1.5 and 2.2mm.

The total thickness of the multilayer structure is generally between 3.5 and 6mm, preferably between 4 and 5mm.

A method for obtaining the multilayer structure according to the invention may also comprise the following steps:
- coating and gelling of a PVC plastisol on both sides of a glass veil in order to obtain a decorative layer and a compact bonding layer, on either side of the glass veil;
- printing of a decoration on the decoration layer;
- coating and gelling of an upper wear layer from a PVC plastisol on the decoration layer;
- coating and gelling of the bonding layer on the compact bonding layer from a PVC plastisol;
- obtaining by calendering, extrusion or pressing and hot laminating the PVC backing layer on the bonding layer, the backing layer having a reinforcing grid entirely embedded on its surface facing the bonding layer;
- coating and gelling of the foamed underlayer on the backing layer from a PVC plastisol.

According to another embodiment, the bonding layer can also be produced by a lower impregnation layer of plastisol, such as a gelled PVC plastisol, and a glass veil which comprises the first reinforcing frame. In this situation, the decoration layer can be printed on a top layer of plastisol, such as PVC plastisol, coated on the glass veil then gelled.

According to particular embodiments, the first and/or the second reinforcing frame is in the form of a glass veil, a glass grid, or a glass grid and veil complex. of glass, in particular to satisfy tests of resistance to the passage of heavy loads and punching.

Other characteristics and advantages of the invention will emerge clearly from the description given below, for information only and in no way limiting, with reference to the appended figures in which:

is a schematic sectional representation of one embodiment of the multilayer structure of the invention.

is a schematic sectional representation of another embodiment of the multilayer structure of the invention integrating a printed decoration layer.

is a schematic sectional representation similar to that of the , the decoration layer being printed on a polymer film.

is a schematic representation, in section similar to that of the , the decoration layer being printed on a glass veil coated on both sides with a PVC plastisol.

is a schematic representation, in section similar to that of the , the structure integrating a second reinforcing reinforcement embedded in the surface of the backing layer and linked to the first reinforcement by a connecting layer.

is a schematic representation, in section similar to that of the , the structure integrating a second reinforcing frame embedded in the back face of the back layer.

is a schematic representation, in section similar to that of the , the multilayer structure integrating a decorative layer, for example conforming to that of the .

Detailed description of the invention

The invention relates to a multi-layer structure (1) with acoustic insulation property, devoid of coupling means and presented in tiles, strips, for the production of a semi-free laying floor covering using a tackifier or double-sided adhesive, or even in glued installation, or presented in rolls, for the creation of a loose-laying floor covering.

The multilayer structure (1) according to the invention can have any shape, in particular as a panel, slab or blade, and can be rolled up on itself or on a mandrel to be presented in a roll.

When presented in a roll, the multi-layer structure has flexibility allowing it to meet the ISO 24344:2008 standard. In this standard, flexibility is defined by the ability of a covering or layer of flooring to be wrapped around a 20mm mandrel, without cracks or cracks forming. Thus, the multilayer structure according to the invention subjected to this test would not present ruptures, cracks, cracks and other permanent defects.

In reference to the , the multilayer structure (1) successively comprises, from the top towards the ground, an upper wear layer (2) of plasticized PVC, a first reinforcing frame (3), a bonding layer (4) of plasticized PVC making it possible to connect the reinforcing reinforcement (3) to a backing layer (5), a compact backing layer (5) of plasticized and filled PVC, and a foamed underlayer (6) of plasticized PVC intended to form the last layer of the structure, particularly with a view to being in contact with the ground.

The upper wear layer (2) allows for control of slipperiness, resistance to wear and ease of cleaning. It comprises 20 to 50 PCR of plasticizer, and has a thickness of between 0.3 and 2 mm, preferably between 0.5 and 1 mm.

The upper wear layer (2) can be obtained by extrusion, by calendering, by pressing, or by coating then gelling a plastisol. The upper wear layer (2) can be coated with a varnish without departing from the scope of the invention, such as a varnish based on polyurethane or urethane acrylate. The upper wear layer (2) can be varnished or grained in order to improve resistance to stains and scratches.

The upper wear layer (2) can also perform the decorative function, particularly if it is obtained from a tinted plastisol or by pressing tinted granules.

The bonding layer (4) comprises 20 to 50 PCR of plasticizer and a loading rate of less than 5% by weight of the bonding layer and has a thickness of between 0.05 and 0.5mm, preferably between 0.1 and 0.3mm. The bonding layer (4) is preferably obtained by coating or is hot rolled after having been obtained by calendering or extrusion. The bonding layer (4) can be related to the upper wear layer (2), in terms of composition and properties, and therefore makes it possible to balance the structure by counterbalancing the curving phenomenon generated by the upper layer. wear (2), with a low weight compared to the backing layer (5) (at equivalent thickness).

Preferably, the upper wear layer (2) and the bonding layer (4) are obtained from plasticized PVC and have the same plasticizer content.

Preferably, and with reference to the , the upper wear layer (2) is transparent or translucent so that a decorative layer (7) is visible through the upper wear layer (2).

In this configuration, the upper wear layer (2) comprises 30 to 50 PCR of plasticizer, and a zero charge rate, or even less than 5% by weight of the upper wear layer (2), and the decoration layer (7) can be printed on a lower face of the upper wear layer (2), or on a coated upper face of the reinforcing reinforcement, or on a polymer film (8) such as a PVC film, see , printed by any known technique and positioned under the upper wear layer (2).

The first reinforcing frame (3) can be a glass grid, a veil of glass fibers.

In order to combine the advantages of the different existing solutions, the frame includes a glass veil, which is complexed with the glass grid by means of a binder, preferably by lamination.

In order to bind the glass veil with the glass grid without complicating the manufacturing process, or unduly weighing down the structure, the binder comprises an acrylic glue, or ethylene-vinyl acetate (“EVA”), or plastisol such as PVC plastisol. Preferably the binder is placed in a thin layer, at a density of between 5 and 35 g/m², or preferably between 10 g/m² to 30 g/m².

For example, the glass veil comprises glass fibers of approximately 10µm in diameter and 10mm in length distributed randomly and linked together by a modified polyvinyl alcohol.

The glass veil generally has a surface mass of between 30 g/m ² and 100 g/m ² . The tensile strength of a reinforcing web is generally chosen to be between 100 N/50mm and 400 N/50mm in the long and transverse directions, measured according to the ISO 1924/2 method.

The wires of a glass grid according to the invention are for example obtained from glass fibers, and are preferably spaced from each other by between 1 mm and 5 mm, preferably by between 2 mm and 4 mm , according to the longitudinal and transverse dimensions, and have a linear mass of between 20 g/m and 110 g/m, advantageously between 35 g/m and 70 g/m. A glass grid generally has a thickness of between 0.1 mm and 1 mm and a surface mass of between 30 g/m2 and 150 g/m2, preferably between 45 g/m2 and 110 g/m2. The tensile strength of a reinforcing grid according to the invention is advantageously between 400 N/50mm and 1000 N/50mm in the long and transverse directions.

The first reinforcing frame (3) makes it possible to improve the dimensional stability of the multilayer structure (1) as well as the resistance to punching. The multi-touch structure according to the invention can claim the U4P3 classification according to the UPEC standard.

The first reinforcing frame (3) can be linked to the decorative layer (7) and to the backing layer (5) by any means, in particular by thermolamination, cold gluing, hot gluing, extrusion of the (s) layer(s) on the first reinforcing frame (3), by powdering hot melt glue or by using double-sided adhesive. If the first reinforcing frame (3) is linked by thermolamination, it directly penetrates the thickness of the backing layer (5) and the decorative layer (7) which then impregnate the first reinforcing frame (3). ).

According to a particular embodiment, see , the first reinforcing frame (3) is a glass veil impregnated on its lower face with a bonding layer in the form of a gelled plastisol (9), such as a PVC plastisol, and on its upper face a plastisol, such as a PVC plastisol, gelled and printed with a decorative layer (7).

The backing layer (5) is made of compact plasticized polyvinyl chloride, i.e. it is not foamed.

The backing layer (5) has a thickness of between 0.4 and 2 mm, preferably between 0.6 and 1.5 mm and is calendered, pressed, or extruded. Generally speaking, a calendered backing layer (4) is preferred because it is easier to integrate recycled material into its composition with this manufacturing technique, without degrading the decor or the appearance of the structure. multilayer (1). The backing layer (5) comprises between 40 and 60 PCR, preferably between 50 and 55 PCR of plasticizer and a loading rate greater than 130 PCR, preferably greater than 150 PCR, more preferably greater than 200PCR and up to 250 PCR .

In reference to the , the multilayer structure (1) preferably comprises a second reinforcing frame (10) to increase the rigidity and improve the dimensional stability and being in the form of a glass veil, a glass grid, or a complex glass grid and glass veil.

The second reinforcing frame (10) is embedded in the surface of the backing layer (4) so as to limit the deformation of the decorative layer (7), and is linked to a lower face of the first reinforcing frame ( 3) by the bonding layer (4) in particular in the form of a plastisol, preferably a PVC plastisol.

Alternatively and with reference to the , the second reinforcing reinforcement (10) is embedded in the back face of the back layer (5) so as to produce a bimetallic effect.

The backing layer (5), preferably calendered, loaded and plasticized, increases the mass and flexibility of the structure, in combination with the bonding layer (4) which makes it possible to stiffen the structure, the stability of the structure is improved and its installation is made easier.

In reference to the , the multilayer structure according to can integrate a decorative layer conforming to that of the .

The plasticizers used in the multilayer structure (1) are of all well-known types, such as Diisononyl Phthalate (DINP), Diisodecyl Phthalate (DIDP), 2-Ethylhexyl Diphenyl Phosphate (DPO), Dioctyl Terephthalate (DOTP), 1,2-cyclohexane dicarboxylic acid diisononyl ester (DINCH), plasticizers of the benzoate family, plasticizers of the adipate family, plasticizers marketed under the PEVALEN® brand by the company Perstorp, epoxidized soybean oil ( HSE), epoxy octyl stearate (ESO), totally or partially biosourced plasticizers such as for example the plasticizers of the polysorb® exeID 37 range marketed by the company Roquette Pharma, the plasticizers of the Citrofol® range marketed by the company Jungbunzlauer International AG, or the plasticizers in the Soft-n-safe® range marketed by the Danisco company. Liquid plasticizers can be used alone or in a mixture.

The fillers used in each layer of the structure may be calcium carbonate, clay, silica, kaolin, or even talc. It is preferably a powdery material to avoid degradation of the filler during mixing of the PVC masterbatch intended to constitute the layers, but it can be considered to use fibers. The fillers can be used alone or in a mixture.

Preferably, the foamed underlayer (6) has a thickness of between 1 and 3mm, preferably between 1.5 and 2.2mm.

The total thickness of the multilayer structure is generally between 3.5 and 6mm, preferably between 4 and 5mm.

Tests were carried out by the Applicant on the following multilayer structure (1), in accordance with the invention, and comprising from top to bottom:
- 0.01 mm acrylic varnish (not shown);
- wear layer (2) in 0.65mm plasticized PVC, obtained by coating with a plastisol;
- connecting layer (9) of 0.6 mm and decorative layer (7) printed of 0.2 mm, on either side of a glass veil (3), obtained by coating with a plastisol;
- bonding layer (4) of 0.2 mm, obtained by coating with a plastisol;
- calendered backing layer (5) of 0.6mm with glass grid on the surface facing the bonding layer;
- foamed underlayer (6) of 2.09 mm, obtained by coating with a plastisol.

The covering comes in the form of strips measuring 1250 mm by 245 mm long. The calendered backing layer comprises approximately 30% by weight of recycled material.

Total thickness: 4.35 mm, surface mass of 3785 g/m ² .

Features
techniques Features Units Example 1 Surface mass g/m2 3785 Total thickness mm 4.35 Wear layer thickness mm 0.65 Backing layer thickness mm 0.6 Thickness under layer mm 2.09 Punching 2h30 mm 0.18 initial curvature mm ≤1 curvature 6h80°C mm 1.7 curvature 72h80°C mm 2.5 curvature 1 month at 23°C mm 1.7 Soundproofing Sticky installation dB 19dB at 23.2°C Sound when walking 63dB at 23.2°C

The above values are values measured according to the following standards:
Total thickness: NF EN ISO 24346 April 2012
Layer thicknesses: NF EN ISO 24340 April 2012
Weight / Surface mass: ISO 23997 December 2007
Curving 6 hours at 80°C: NF EN ISO 23999 August 2018
Curving 72 hours at 80°C: NF EN ISO 23999 August 2018
Monitoring of the curvature 1 month at 23°: NF EN ISO 23999 August 2018
Remanent static punching (Building): ISO 24343-June 1, 2007
Acoustic attenuation: NF EN ISO 717-May 2, 2013 and NF EN ISO 10140-July 3, 2021
Walking sound less than 65 according to NF EN 16205 August 2013 / NF EN 16205/IN1 May 2018 / NF S 31-074.

It appears from the above that the invention provides a multilayer structure (1) for the production of a floor covering, which is balanced and stable and which presents satisfactory acoustic insulation performance in pegged installation, while reducing environmental impact.

Claims (11)

Multi-layer structure (1) for producing a floor covering, the multi-layer structure (1) is devoid of coupling means and successively comprises:
- an upper PVC wear layer (2) comprising 20 to 50 PCR of plasticizer, and having a thickness of between 0.3 and 2 mm, preferably between 0.5 and 1 mm;
- a first reinforcing frame (3);
- a bonding layer (4) of plasticized PVC making it possible to bond the reinforcing frame (3) to a backing layer (5);
- said backing layer (5), which is made of compact PVC and comprising 40 to 60 PCR of plasticizer, and a loading rate greater than 130 PCR, or even greater than 150 PCR, or even greater than 200 PCR and up to 250 PCR ;
- a foamed underlayer (6) in plasticized and loaded PVC;
characterized in that the backing layer (5) has a thickness of between 0.4 and 2 mm, and in that the bonding layer (4) comprises from 20 to 50 PCR of plasticizer and a loading rate of less than 5% by weight of the bonding layer (4) and has a thickness of between 0.05 and 0.5mm. Multilayer structure (1) according to claim 1, characterized in that the upper wear layer (2) is transparent, comprises 30 to 50 PCR of plasticizer, and a loading rate of less than 5% by weight of the upper layer ( 2), and in that the multilayer structure (1) comprises a decorative layer (7) positioned under the upper wear layer (2). Multilayer structure (1) according to claim 2, characterized in that the decoration layer (7) is a layer of ink printed on a lower face of the upper wear layer (2), or on an upper face coated with the first reinforcing frame (3), or on an upper face of a decorative film positioned under the upper wear layer (2). Multilayer structure (1) according to claim 1, characterized in that the upper wear layer (2) is a layer of pressed granules. Multilayer structure (1) according to one of the preceding claims, characterized in that it comprises a second reinforcing frame (10) in the form of a glass veil, a glass grid, or a complex glass grid and glass veil. Multilayer structure (1) according to one of the preceding claims, characterized in that it comprises a second reinforcing frame (10), embedded in the surface of the backing layer (5), and linked to a lower face of the first reinforcement reinforcement by the bonding layer. Multi-layer structure (1) according to one of claims 1 to 5, characterized in that it comprises a second reinforcing reinforcement (10), embedded on the reverse side of the reverse layer (5), at the surface of the underlayer. Multilayer structure (1) according to one of the preceding claims, characterized in that the underlayer (6) has a thickness of between 1 and 3mm. Multilayer structure (1) according to one of the preceding claims, characterized in that the bonding layer (4) is a layer of plastisol, such as a PVC plastisol. Multilayer structure (1) according to one of the preceding claims, characterized in that the backing layer (5) has a thickness of between 0.6 mm and 1.5 mm. Multilayer structure (1) according to one of the preceding claims, characterized in that the first and/or the second reinforcing frame (9) is a glass veil, a glass grid, or a glass grid and glass veil complex. glass.