Patent Application
20250171953
The present invention pertains to a method for manufacturing a carpet product, which method typically comprising providing a sheet having a front surface and a back surface as a primary backing, and one or more yarns stitched through this first sheet to form a pile on the front surface of this primary backing. At the back surface, the one or more yarns are locked to the primary backing, typically by applying a latex or other adhesive. In particular, the invention pertains to a method that leads to a carpet product that is suitable for commercial use, i.e. a product of class 31 (Moderate Commercial Use), 32 General Commercial Use) or 33 (Heavy Commercial Use) according to the European norm EN 1307:2014+A3:2019 (including the Vetterman test according to ISO 10361:2015). The invention also pertains to a carpet product that is obtainable with a manufacturing method according to the invention.
In the present-day world carpeting is used for multiple purposes. An important reason for using carpet products is esthetics. Other purposes are (walking) comfort, noise attenuation and hygiene. Considerations to take into account when making a carpet product for a specific purpose however also include the weight of the carpet product, the cost of the product, the feel (or the “hand”) of the product and importantly, durability. High end carpet products are typically tufted constructions. Tufted carpet products generally include a composite structure in which tufts, or bundles of carpet fibers are introduced (such as by stitching) into a primary backing, such as a woven or non-woven fabric. These carpet fibers are typically a yarn consisting of nylon, polyester, wool or polypropylene, with nylon being the most common. A secondary backing or coating of thermoplastic material is then commonly applied to the underside of the carpet construction in order to securely retain the tufted material in the primary backing. This secondary backing not only dimensionally stabilises the carpet product but may also provide greater abrasion and wear resistance, and may serve as a basis for adhering an additional layer of material. Tufted nylon carpet has superior wear characteristics and as a result is generally preferred in commercial applications (such as e.g. in stores, hotels, conference centers, restaurants, offices, cars, air terminals, trains, aircraft, elevators and entrance areas) versus the less superior wear of polyester carpet products. Nylon however has some drawbacks. Apart from being relatively expensive, it is not easy to recycle (it needs chemical recycling) and is more sensitive for staining. Also, dimensional stability is not optimal. In that respect, polyester, in particular polyethylene terephthalate (PET) seems a better alternative, being relatively inexpensive, easy to recycle, with a natural stain resistance and potentially a better dimensional stability. However, the wear resistance of carpet made with polyester yarns is too low to arrive at a product suitable for commercial use. Polyester based carpet is thus mainly used for domestic applications.
In the art, several attempts have been made to arrive at a carpet product using polyester yarns, which product has an improved durability. For Example, US 2020/0190718 (assigned to Invista North America S.A.R.L, Wilmington, USA) discloses a carpet with self-twisted loop piles that has an appearance and esthetics similar to a cut pile carpet products but with improved durability. For this the carpet product comprises a single yarn (a so-called 1-ply yarn) twisted at a higher twist level than typically used which is stitched through a preconstructed woven or nonwoven fabric backing to form a loop or a tuft. Due to the high twist level the loop pile gets automatically twisted. It is described that the 1-ply yarn is twisted in the range of 1 to 15 turns per inch (tpi), which equals 40-600 tpm (turns per meter), in particular 200-400 tpm. The single yarn is directly tufted into carpet without a yarn heat setting step. Although the PET carpet passes the Vetterman test to arrive at a high quality carpet product in this respect, a disadvantage of the high twisting level is that the tuft bind strength is relatively low such that overall durability is still below what is needed for (high end) commercial use. Also, the self-twisted 1-ply yarns provide an appearance that is not appreciated in all markets.
WO96/35836 (assigned to 3M, Saint Paul, USA) describes a carpet product that is capable of withstanding significant pedestrian traffic and is useful for placement at the entryway of a building, for example, to wipe wet and/or dirty shoe soles. It is described that polyester yarns can be used to manufacture the carpet product. The product comprises a pile layer of tufted bundles of textured synthetic resinous filaments, each filament having a linear density of at least 800 denier, the filaments in each tufted bundle arranged in loops of random shapes and orientations and intermingled with loops in adjacent tufted bundles of filaments in the pile layer. The pile layer has a thickness when measured outward from the surface of the substrate of at least 5 mm and preferably between 5 mm and 15 mm. This way, a heavy carpet product is produced that has the ability to retain soil and which is resilient and durable enough to withstand pedestrian traffic without significant deterioration. This makes the product very suitable for an outdoor mat or rug. However, the high pile prevents that the product maintains its initial esthetic appearance and thus is not suitable for high end indoor applications.
CN10228619 discloses a colored glossy and elastic fine denier carpet and manufacturing method high end domestic use. The carpet uses yarns having a relatively high weight (DTex above 2400), and a twist level of about 50-130 tpm. The combination of a high weight yarn and a high twist level provides good appearance and resilience. However, durability is too low to meet the requirements for commercial applications.
US 2008/0220200 (assigned to Futuris Automotive Interiors Inc., Troy, USA) discloses a PET carpet product that is suitable as a carpeting for the interior of cars. For this a tufted PET carpet product is described comprising a pile of PET yarn comprised of PET fibers and tufted at a pre-determined gauge into a first backing layer, the pile layer having a particular face weight, a back coating layer of an adhesive adjacent the first backing and an underlayment layer adjacent the second backing layer. The backing adhesive is applied using an extrusion process to lock the tufted PET to the backing, and steam is applied to the tufted PET to enhance the look and feel of the PET. This leads to a product suitable for use in cars. However, the method is rather complicated making the product relatively expensive.
US 2016/0136844 (assigned to Milliken & Company, Spartanburg, USA) discloses a 100% polyester fully recyclable carpet, using a very high viscosity polyester adhesive to securely bond the tuft yarns. However, fuzz-resistance is still relatively low (Velcro rolling fuzzing resistance of 2 or less). At higher fuzzing resistance (4) there is no adhesive left to bond a secondary backing. This makes the carpet less attractive for high end uses.
It is object of the invention to provide an improved method to manufacture a carpet product that is easy to recycle yet is suitable for commercial use, in particular meeting at least class 31 of European norm EN 1307:2014+A3:2019, preferably class 32 or 33. It is another object to provide such a carpet product.
In order to meet the object of the invention, a method to manufacture a carpet product is devised, the method comprising providing a first sheet having a front surface and a back surface (which sheet is commonly denoted as the primary backing), providing one or more polyester yarns having a weight of at least 2500 Dtex (such as for example at least 2500, 2550, 2600, 2650, 2700, 2750, 2800, 2850, 2900, 2950, 3000, 3050, 3100, 3150, 3200, 3250, 3300, 3350, 3400, 3450, 3500, 3550, 3600, 3650, 3700, 3750, 3800, 3850, 3900, 3950, 4000, 4100, 4200, 4300, 4400, 4500, 4600, 4700 4800, 4900, 5000, 5100, 5200, 5300, 5400, 5500, 5600, 5700, 5800, 5900, 6000, 6100, 6200, 6300, 6400, 6500, 6600, 6700, 6800, 6900, at least 7000 or even above) and a twist level of at least 100 tpm (such as for example at least 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 220, 230, 240, 250, 260, 270, 280, 290, at least 300 or even above), forming a pile on the front surface of first sheet by stitching the one or more yarns through the first sheet, the one or more yarns having a free end that forms the said pile and a locked end present at the back surface of the first sheet, thereby forming an intermediate product, processing the intermediate product by feeding this product along a body having a heated surface, the back surface being contacted with the said heated surface, to melt at least a part of the polyester of the locked end of the one or more yarns, and cooling the molten part of the polyester to solidify this molten part of the polyester, thereby connecting the locked end of the one or more yarns to the first sheet and forming the carpet product.
Polyester yarns are inherently easy to recycle, as is commonly known in the art. Mechanical recycling is an option, as is one of the many known processes for chemical recycling such as those used for recycling polyester bottles (e.g. as disclosed in WO 2022/003084, assigned to Cure Technology BV). The durability requirements for meeting commercial standards are surprisingly met by combining a relatively high weight (also denoted as “count” or “titer”) of the polyester yarns (above 2500 Dtex), with a relatively high twist level (above 100 tpm) and a method to connect the yarns at the back of the primary backing by melting instead of using a coating such as latex. Such a method for connecting polymer yarns to a primary backing per se is known in the art, i.a. from WO 2012/076348 (assigned to Niaga BV), but not in combination with the other features to arrive at a product that meets the requirements for high end commercial use. It appears that when combining these three technical features (particular Dtex level, twist level, and binding the yarns by melting) when using polyester yarns, the object of the invention can be met, in particular, one is able to provide a carpet product that meets at least class 31 of European norm EN 1307:2014+A3:2019, and even class 32 or 33 depending on the (other) characteristics of the carpet product.
Although it is not completely clear why the combination of these features provides the desired effect for a carpet product using polyester yarns, it is believed that the high twist level at least partly compensates for the lack of inherent resilience of the polyester yarns. The relatively high Dtex value on its turn appears to be able to compensate for the loss of fluffiness due to the high twist level. Importantly, it was applicant who recognised that typically a high twist level is disadvantageous for arriving at a proper filament binding level. This may be due to the fact that adhesives can penetrate less efficient into the yarns. However, the melting and colling down feature for bonding the yarns at the back as used in the present manufacturing method does not have this disadvantage. On the contrary, the higher the density of the yarns, the better the heat conduction and thus melting process may take place.
Although it was found that meeting the Dtex and tpm value as recited here above enables the provision of a carpet product suitable for (high) end commercial use, it is particularly preferred that the tpm level (at a Dtex value above 2500) meets the following relation with the value for the weight of the yarns:
If the tpm level is indeed above the value according to this formula (60000/(Dtex-2500)+100), combinations of a relatively low tpm and low Dtex value (within the invention) can be avoided such that there is more freedom for other characteristics of the carpet product such as gauge (distance between needles per inch), stitch rate (number of stitches per inch in the length of a carpet product), pile height, number of filaments in the yarns, ply of the yarns, dpf etc.
In line with the method as described here above, the invention also pertains to a carpet product comprising a first sheet having a front surface and a back surface and one or more polyester yarns stitched through the first sheet, forming a pile on the front surface of the sheet, which yarns have a weight of at least 2500 Dtex and a twist level of at least 100 tpm, wherein at least a part of the polyester of the locked end of the one or more yarns is molten, spread over the back surface of the sheet and solidified.
A yarn is a unitary textile wire or thread that can be used in a stitching process. Typically, a yarn consists of a bundle of twisted strands of fibres, which fibres on their turn consist of a bundle of entangled filaments.
A multiply yarn is a yarn that is composed of multiple strands that are twisted together as one yarn. Three-ply yarn for example, is composed of three single strands that are twisted together.
A polyester product is a product that consist at least for more than 50 mass % out of a polyester polymer, preferably at east 55, 60, 65, 70, 75, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89l 90, 91, 92, 93, 94, 95, 96, 97, 98, 99 up to 100 mass %.
A polyester is a category of polymers that contain the ester functional group in every repeat unit of their main chain (Köpnick H, Schmidt M, Brügging W, Rüter J, Kaminsky W (June 2000). “Polyesters”. Ullmann's Encyclopedia of Industrial Chemistry. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA.). Examples of polyester are Polycaprolactone (PCL), Polylactic acid (PLA), Polyhydroxybutyrate (PHB), Polyglycolic acid (PGA), Polyethylene adipate (PEA), Polyethylene terephthalate (PET; such as Mylar®, Rynite® and Impet®), Polybutylene terephthalate (PBT; such as Crastin® and Celanex®,), Polyethylene naphthalate (PEN), Polytrimethylene terephthalate (PTT; such as Sorona®), Polyester of 4-hydroxybenzoic acid and 6-hydroxynaphthalene-2-carboxylic acid (LCP), Polyester of Bisphenol A and phthalic acid (PAR).
Dtex (or dtex) is the mass (weight) of a (single) yarn in gram per 10,000 m. In the art this is also denoted as (total) yarn count or titer and is the total mass of a final yarn after twisting.
Dpf is denier per filament, wherein denier is the weight in grams of 9,000 meters of an individual filament.
A twist level of a yarn is the total number of twists as present per meter of yarn, i.e. the number of bumps in a yarn per meter divided by the ply number (Berka, Amanda (Winter 2007), “Technically Speaking: Twists Per Inch”, SpinOff Magazine, Interweave, pp. 11-12).
A carpet product is a relatively thick textile product used for covering a floor or another object which is tread upon such as the interior of a car. Typical carpet products are broadloom carpet, carpet tiles, mats and rugs
A sheet is a substantially two dimensional mass or material, i.e. a broad and thin, typically, but not necessarily, rectangular in form.
Fibrous means consisting basically out of fibres. “Basically” means that the basic mechanical constitution is arranged out of fibres: the fibres may however be impregnated or otherwise treated or combined with a non-fibrous material such that the end material also comprises other constituents than fibres. Typical fibrous sheets are woven and non-woven textile products, or combinations thereof.
Stitching is a method of mechanically making a yarn part of an object by stitches or as if with stitches, such as by tufting, knitting, sewing, weaving etc.
A felted layer is a layer of non-woven separate fibres which are matted together using mechanical impact, optionally using heat and moist.
A hot melt adhesive is a thermoplastic adhesive that is designed to be melted, i.e. heated to undergo a first order transition to transform from a solid state into a liquid state to adhere materials after solidification. Hot melt adhesives are typically non-reactive, (at least partly) crystalline and comprise a low amount of or no solvents (0-5 m %, preferably 0-2 m % or even 0-1 m %) so curing and drying are typically not necessary in order to provide adequate adhesion.
Intrinsic viscosity {\displaystyle \left[\eta \right]} is a measure of a solute's contribution to the viscosity η of a solution, see “Progress in Biophysics and Molecular Biology” (Harding 1997). The IV can be measured according to DIN/ISO 1628. Typically, a concentration of 1% for the polymer is used and m-cresol as solvent, wherein the IV can be expressed in dl/g (often presented without the latter dimension). {\displaystyle \left[\eta \right]=\lim _{\phi \rightarrow 0}{\frac {\eta −eta _{0}}{\eta _{0}\phi}}}A practical method for the determination of intrinsic viscosity is by using an Ubbelohde viscometer.
In a first embodiment of the method according to the invention the one or more polyester yarns have a weight of at least 2800 Dtex and a twist level of at least 120 tpm. At this level of Dtex and tpm, in combination with the melting step of the yarns at the back, even improved durability properties can be obtained, enabling the manufacturing of a carpet product that meets class 32 and 33 (according to European norm EN 1307:2014+A3:2019). Although it was found that meeting these Dtex and tpm values enables the provision of a carpet product suitable for high end commercial use, it has been found that it is particularly preferred that the tpm level (at a Dtex value above 2800) meets the following relation with the value for the weight of the yarns:
If the tpm level is indeed above the value according to this formula, combinations of a relatively low tpm and low Dtex value (within the above embodiment) can be avoided such that there is more freedom for other characteristics of the carpet product such as gauge, stitch rate, pile height, number of filaments in the yarns, ply of the yarns, dpf etc.
In a second embodiment of the method according to the invention the one or more polyester yarns have a weight of at least 3000 Dtex and a twist level of at least 150 tpm. At this level of Dtex and tpm, in combination with the melting step of the yarns at the back, even further improved durability properties can be obtained, enabling the manufacturing of a carpet product that even meets class 33 (according to European norm EN 1307:2014+A3:2019).
In yet a next embodiment of the method according to the invention the first sheet is a polyester sheet. This has the advantage that the product is even more easy to recycle since the yarns and the sheet do not need to be separated for recycling and can be processed as one, for example by shredding and thereafter melting the shredded product, optionally followed by a chemical process.
In yet another embodiment the polyester comprises PET (polyethylene terephtalate) and/or PTT (polytrimethylene terephthalate). These types of polyester, either alone or in combination were found to be particularly suitable for manufacturing a carpet product. PET has the advantage that it is readily available as recycled material at a low price and still is able to meet high quality standards enabling the use for producing high quality yarns for textile applications, even high end carpet applications. For this it is preferred that the polyester has an intrinsic viscosity above 0.8 dl/g (which is typical for a bottle grade product of PET). The higher the iv, the better the polymer is used for producing high quality yarns and thus high end carpet products. Moreover, it is advantageous that in the carpet product only one type of polyester is used for both the yarns and the sheet, and optionally other polymer containing parts of the product.
In again another embodiment of the method according to the invention, the one or more yarns are multi-ply yarns, in particular 2, 3 or 4 ply. It was found that with a multiply yarn it is easier to apply higher twist levels and thus to arrive at a higher class of durability in the present invention. A single ply yarn at a high twist level (typically above 120) becomes self-twisting which is disadvantageous for many applications.
In yet again another embodiment of the method according to the invention, the one or more yarns are each composed of multiple filaments having a weight of between 2 and 40 dpf. This low dpf value may lead to a more comfortable hand, while at the same time still being able to meet the desired durability requirements. This probably has to do with the higher flexibility of the filaments. Preferably, the filament weight is between 5 and 20 dpf, even more preferably between 8 and 12 dpf such as 8, 9, 10, 11 or 12 dpf.
In still another embodiment of the method according to the invention, the one or more polyester yarns have a weight of at least 3500 Dtex, preferably at least 4000 Dtex. It was found that at this weight the durability could be further increased. For nylon carpet product such weight are hardly applied due to the cost of goods.
In yet another embodiment of the method according to the invention, the step of processing the intermediate product by feeding this product along a body having a heated surface, the intermediate product has a relative speed (not being zero) with respect to the heated surface of the body. In this embodiment the molten fraction of the yarns is spread in a direction parallel to the surfaces of the first sheet by imparting a mechanical force on the molten fraction in the said direction. This mechanical force may lead to a calendaring process, virtually uniting the (molten) yarn ends at the back of the intermediate product into one continuous and smooth layer of material. This improves the tuft bind and hence the durability properties of the resulting carpet product.
In another embodiment of the method according to the invention, the method comprises connecting a second sheet to the carpet product, using an adhesive applied between the processed back surface of the first sheet and the second sheet. By applying a second sheet, commonly referred to as the secondary backing, the dimensional stability of the product can be improved, as well as the (walking) comfort and/or the ease of laying the product.
Preferably, the adhesive is a hot melt adhesive. A hot melt adhesive, due to its crystalline properties, is relatively brittle when cold. As such, it was expected that the local deformation of the intermediate product would lead to breakage of the adhesive and hence delamination. This does not appear to be the case. In a further embodiment the hot melt adhesive is a polyester adhesive. This is advantageous for the recycling of the carpet product which already comprises polyester yarns.
In another embodiment of the method according to the invention, the second sheet is a fibrous sheet, preferably a felted sheet. Most preferably the second sheet is a polyester sheet.
It is noted that any of the above features of the embodiments of the method according to the invention, correspond to embodiments of the resulting carpet product.
The terms Fig., Figs., Figure, and Figures are used interchangeably in the specification to refer to the corresponding figures in the drawings.
The invention will now be explained in more detail using the following non limiting examples that disclose particular embodiments of the invention and comparative examples.
As depicted in
Example 1 describes various carpet products according to the invention. The yarns used are all PET yarns, plied, twisted and heat set after twisting (as commonly done in the art to more or less secure the twists). The primary backings are in each case woven PET backings, obtained from firms as indicated in Table 1. The primary backings all have a cap as described with reference to
The resulting carpet products were all subjected to a classification test according to European standard EN1307:2014+A3:2019, including the commonly known Vetterman test. This test may lead to a qualification as follows:
The products of the invention all met the classification for Commercial use, even reaching class 32 and 33 for some products, in particular at a combination of a Dtex of 3000 or higher and a twist level of 144 or higher. As is commonly known, the gauge and stitch rate have hardly any influence on the obtained class, in particular when typical rates are applied such as 5/32″ to 1/12″, such as for example the common ⅛″ and 1/10″, for the gauge and between 10 and 70, such as for example the common 30-60, in particular 38-44, for the stitch rate. The stitch rate tested was chosen because this fits best with the used fibre binding technology. A higher stitch rate also typically is beneficial for the Vetterman test results.
In this example various comparative examples are described and depicted in Table 2.
The materials used for the comparative examples are the same as used for the examples according to the invention and also, the fibre-binding process has been applied the correspondingly. The differences are due to differences in Dtex of the stitched yarns, in combination with a lower twist rate (at a level in line with common nylon carpet tiles to reach commercial class 31, 32 and 33). As can be seen, this leads to lower classification.
In this example, apart from re-using the yarns as such (by cutting and making a new carpet product with the yarns), several methods are described for fully recycling a carpet product according to the invention. None of these methods requires separation of the carpet product into various polymer containing materials since all carpet products according to Table 1 (and also those of Table 2) are pure PET products in the sense that all polymer material used in the products (yarns, primary backing, secondary backing, adhesive) is polyethylene terephthalate.
This provides various relatively easy options for recycling the products for circular use (as opposed to process such as pyrolysis, decarbonisation and using the PET as an additive in for example stone mastic asphalt, cementitious materials, mortars or concrete composites etc.).
The methods all include primary steps wherein the carpet product is firstly cut into smaller pieces that enable easy uptake in recycling methods.
A first example of a class of processes that allows circular use of the polyester are processes based on (thermo-) mechanical methods to recycle polyester waste material. The simplest way of thermo-mechanical recycling is re-melting the polyester waste. This method is applied for example in bottle-to-bottle technologies, where sorted PET-bottles are re-melted in crushed shape and reprocessed to bottles as beverage packaging.
A second class of processes to recycle polyester waste are the so-called chemical recycling (chemolysis) processes, wherein recycling of polyester waste material is enabled by depolymerisation into monomers and/or oligomers. This class can be divided in numerous sub-classes depending on the type of reactant used for the chemolysis.
An example is the application of ionic liquids for de-polymerization, first described around the year 2000. This method was developed to avoid the drawbacks of other methods like alcoholysis (high pressure and temperature as well as a heterogeneous reaction product) or acidic and alkaline hydrolysis (pollution problems) to provide an eco-friendly degrading agent for polymers and to enable degradation under moderate reaction conditions.
As an alternative castor oil is applied for de-polymerisation. This method was developed to provide a renewable substitute of petrochemical agents (for example, glycols) for PET de-polymerization. After de-polymerization, the reaction products were aimed for the preparation of polyurethane systems.
The degradation of polyester polymers using enzymes was first described in the 1970's. As the use of ionic liquids and castor oil, this bio-chemical method was developed to provide an eco-friendly procedure of polymer recycling in contrast to conventional chemical recycling methods.
Alcoholysis for de-polymerization of PET was first described in the early 1990's. This method was developed to avoid the drawbacks of the acidic and alkaline hydrolysis (pollution problems) to provide a renewable and more eco-friendly degrading
agent for polymers. Generally, polyester is de-polymerised with an excess of
an alcohol to yield corresponding esters of the corresponding acid and ethylene glycol. Among the alcoholysis methods, reaction with methanol has gained special importance because of the low price and the availability of methanol. Also ethylene glycol (a diol, the use of which is sometimes classed separately as “glycolysis”, although it falls in the class of alcoholysis) is used mainly in reactive extrusion to produce low molecular weight oligomers. However, these oligomers have to be separated and purified for further processing, since the crude reaction product consists of a heterogeneous mixture of monomer, oligomers and polymers. Various other alcohols are described to be useful such as pentaerythritol, 1-butanol, 1-pentanol and 1-hexanol and 2-ethyl-1-hexanol. Also other diols than ethylene glycol, like BHET, neopentyl glycol (NPG), tetraethylene glycol (TEEG), polyethyleneglycol, polytetramethylene oxide and terpoly[poly(oxyethylene)-poly-(oxypropylene)-poly(oxyethylene) are described in the art for depolymerizing polyester by alcoholysis. An improved method of alcoholysis has been described in recent patent application WO2022/003084 (assigned to Cure Technology BV) in which method in a first stage of two consecutive stages, a stream of polyester waste material is continuously fed to an extruder operated at a temperature above the melting temperature of the polyester, while alcohol is fed to the extruder, and in a second stage, the fluid mixture is continuously fed to a continuously stirred tank reactor (CSTR) operated at a temperature above the melting temperature of the polyester, while co-feeding a second amount of alcohol to the CSTR, to provide at the outlet of the CSTR a continuous stream of polyester depolymerised into an oligomeric ester. The oligomers can be used to make new polyester of any quality.
Aminolysis and ammonolyis were developed for polyester recycling, since the reactivity of the amine-group is higher than the hydroxyl-group or alcohols used alcoholysis of polyester.
Lastly, an alternative chemical recycling of polyester is given by the controlled de-polymerization of polyester using blocking chain scission with defined amounts
of the de-polymerization agent (see Geyer et al. in eXPRESS Polymer Letters Vol. 10, No. 7 (2016) 559-586). This method produces polyester oligomers of well-defined molecular weights in a greater range than existing chemical methods like alcoholysis.
| Number | Date | Country | Kind |
|---|---|---|---|
| 22159279.3 | Feb 2022 | EP | regional |
This application is the United States national phase of International Patent Application No. PCT/EP2023/054714 filed Feb. 24, 2023, and claims priority to European Patent Application No. 22159279.3 filed Feb. 28, 2022, the disclosures of which are hereby incorporated by reference in their entireties.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2023/054714 | 2/24/2023 | WO |
