FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
&
THE PATENTS RULES, 2003
As amended by the Patents (Amendment) Rules, 2006
COMPLETE SPECIFICATION (See section 10 and rule 13)
TITLE OF THE INVENTION A PROCESS OF PREPARING A POLYLACTIC ACID TAPE YARN
APPLICANTS Aditya Birla Science and Technology Company Pvt Ltd
of address
Plot No 1 and 1-A/1, Taloja, MIDC, Taluka-Panvel, District Raigad Maharashtra – 410208, India
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes this invention and the manner in which it is
to be performed:

FIELD OF THE INVENTION
The invention is directed to materials comprising polylactic acid. In particular, the present invention relates a process of preparing biodegradable slit tape yarns made of polylactic acid (PLA) and methods of preparation thereof.
BACKGROUND ART
Conventionally, slit tape yarns are manufactured from non-biodegradable petroleum-based synthetic resin such as polyethylene (PP) and high density polypropylene (HDPE) by film slitting technology. These tape yarns have excellent mechanical properties and so are widely used in packing of cement, fertilizers, chemicals, plastic granules, grains, etc. [003] However, since the conventional tape yarns are formed of petroleum-based synthetic resin materials (PP/HDPE), if discarded in the natural environment after use, they will not decompose. Improper disposal of the tape yarns made from these non¬biodegradable materials also causes the problem of micro-plastic particle generation leading to contamination of soil and water bodies.
The problem of waste disposal can be significantly mitigated by switching from petroleum-based plastics to bioplastics that are biodegradable and/or compostable. Polylactic acid (PLA) is one such bioplastic.
Polylactic acid (PLA) is biodegradable hydrolyzable aliphatic semicrystalline polyester produced through the direct condensation reaction of its monomer, lactic acid, as the oligomer, and followed by a ring-opening polymerization of the cyclic lactide dimer. One of the key properties of PLA is that it is biodegradable, viz. it can break down when composted under influence of enzymatic action in the course of time.

Although PLA is a thermoplastic polymer similar to PP/HDPE, it differs in terms of melting temperature, glass transition temperature (Tg), melt rheology, crystallization rates, etc. Due to these differences, it is not an easy task to produce PLA tapes on a conventional tape yarn plant suited for PP/PE. It is furthermore well known, that spinning and drawing of high-strength PLA objects becomes increasingly difficult the higher the molecular weight, and intrinsic viscosity of the polylactic acid. In view of drawbacks, a number of methods are proposed to prepare slit yarn made of a biodegradable polylactic acid.
US20190284726A1 recites a process for making high-strength polylactic acid elongated object comprising the steps of making a solution of polylactic acid in a solvent at a concentration of 5 to 50 mass %; spinning the solution through a spinplate comprising at least 1 spinhole to form a fluid elongated object; cooling the fluid elongated object with a cooling medium to form a solvent-containing gel elongated object; removing at least partly the solvent from the gel elongated object to form a solid elongated object; and drawing the elongated object while applying a draw ratio of at least 2, to form a high strength PLA elongated object, characterized in that the cooling medium has a temperature Tq of less than 0° C.
US9440393B2 recites a process for producing a product, comprising the steps of: (a) feeding PLA material wherein more than 95 wt % is PLA to an extruder; (b) cooling the extruded PLA material to a temperature of 15-45° C; (c) optionally cutting the cooled material into two or more strips; (d) a first stretching step, wherein the material is fed to a first roller, then to a first oven, where it is heated to a temperature of 75-95° C, and then to a second roller, wherein the roller speed of the second roller is higher than the roller speed of the first roller; (e) a second stretching step, wherein the material is fed to a third roller, then to a second oven, where it is heated to a temperature of 95-120° C, and then to a fourth roller, wherein the speed of the fourth

roller is higher than the speed of the third roller. Although, US9440393B2 describes
the process of manufacturing PLA tapes the process has following limitation: (1) PLA
with Tg< 60°C cannot be converted to tapes, (2) the tapes cannot be stretched to
higher than 1:4 draw ration in a single stretching step, thus two stretching steps are
required.
Although proposed, since polylactic acid is hard and brittle and it is difficult to form a
tape yarn using conventional methods.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method for producing tape yarn from polylactic acid. [002] In an aspect, the present invention provides a process of preparing a polylactic acid tape yarn, comprising:
a) melting a blend of polylactic acid and at least one filler material in an extruder;
b) extruding said blend of molten polylactic acid and filler through a die to obtain a film of polylactic acid;
c) passing said film of polylactic acid through water at a temperature in the rangeof20°Cto90°C;
d) splitting said film of polylactic acid in to tape; and
e) stretching the tape in a hot air oven to yield polylactic acid tape yarn.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing summary, as well as the following detailed description of the invention will be better understood when read in conjunction with the appended drawings. For the purpose of assisting in the explanation of the invention, there are shown in the

drawings embodiments which are presently preferred and considered illustrative. It
should be understood, however, that the invention is not limited to the precise
arrangements and instrumentalities shown therein. In the drawings:
FIG 1 shows the process flow diagram of tape yarn manufacturing process from
PP/HDPE
FIG 2 shows the schematic of tape yarn manufacturing unit
FIG 3 shows the process flow diagram of tape yarn manufacturing process from PLA
of present invention
DESCRIPTION OF THE INVENTION
In describing and claiming the invention, the following terminology will be used in accordance with the definitions set forth below. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, the preferred methods and materials are described herein. As used herein, each of the following terms has the meaning associated with it in this section. Specific and preferred values listed below for individual process parameters, substituents, and ranges are for illustration only; they do not exclude other defined values or other values falling within the preferred defined ranges.
As used herein, the singular forms "a," "an," and "the" include plural reference unless the context clearly dictates otherwise.
The terms "preferred" and "preferably" refer to embodiments of the invention that may afford certain benefits, under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances.

Furthermore, the recitation of one or more preferred embodiments does not imply that
other embodiments are not useful, and is not intended to exclude other embodiments
from the scope of the invention
As used herein, the terms "comprising" "including," "having," "containing,"
"involving," and the like are to be understood to be open-ended, i.e. to mean including
but not limited to.
Until now, it is believed that products such as tapes, films, yarns, etc. from polylactic
acid could not be stretched on an industrial scale, since the products are very
susceptible to breakage. If the aforementioned polylactic acid products are rolled up in
an industrial stretch apparatus, for example, of the type shown in figure 1, it was
believed that no operation on an industrial scale is possible, unless special measures
are taken, as the product could break before stretching is carried out. The process of
figure 1 is carried out in a tape yarn manufacturing unit as shown in figure 2.
The present inventors have accomplished the present invention as a result of intensive
research to solve the above problems. The glass transition temperature (Tg) of
polylactic acid is in the range of 55-60°C, which is well above the room temperature.
Hence, the PLA film coming out of water bath at lower temperatures (~30-35°C) are
brittle.
The problem was overcome by raising the temperature of the water bath more than the
Tg of PLA as shown in the process diagram shown in figure 3. According to the
present invention, this is provided by a process characterized in that in the step of
cooling (also called quenching) the fluid elongated object, the cooling medium has a
temperature (Tq) in the range of 50°C - 65° C.
In an embodiment, the invention provides a process of preparing a polylactic acid tape
yarn, comprising:
a) melting a blend of polylactic acid and at least one filler material in an extruder;

b) extruding said blend of molten polylactic acid and filler through a die to obtain a film of polylactic acid;
c) passing said film of polylactic acid through water at a temperature in the range of 40°C to 90°C;
d) splitting said film of polylactic acid in to tape; and
e) stretching the tape in a hot air oven to yield polylactic acid tape yarn.
In an embodiment, optionally the blend of step (a) optionally comprises of at least
one additive.
In an embodiment the filler material is selected from a group consisting of calcium
carbonate, talc, silicates, clay, preferably calcium carbonate. In an embodiment, the
range of filler material is in the range of 5-15%.
In an embodiment, the temperature of water bath, it can be varied between the glass
transition temperature (Tg) and crystallization temperature (Tcc) of the PLA polymer
i.e. Tg < Water bath temperature < Tm, to keep the film flexible enough for the
extrusion in the range of 40°C to 90°C, more preferably in the range of 50°C to 80°C.
In an embodiment, quenching of film at step (c) is carried out using heated rollers or
hot air. In an embodiment, liquids other than water may be used in the quenching of
film at step (c).
In an embodiment, slitting of film at step (d) is performed by a tape slitter. The
stretching of tape at step (e) may be carried out in more than one stage. In an
embodiment, the temperature during the stretching is maintained in the range of 90°C-
140°C.
The increase in the temperature of water bath for the PLA film making is the key
process parameter. This differentiates the process of present invention from the
conventional method of PP/HDPE processing on a tape manufacturing unit. The
extrusion of a film in a hot water bath eliminates the brittleness of the extruded film

and allows subsequent slitting into tapes, hot stretching and annealing to impart
improvement in tensile properties necessary for woven fabric preparation.
With the process according to the invention elongated tape yarn could be
manufactured from PLA having an elongation at break in the range of about 8-30%.
In addition, the draw ratio of the tape yarn in a single stretch is in the range of 1:3 to
1:8.
WORKING EXAMPLES
The following specific examples are illustrative and explanatory of the present invention but are not to be construed as limiting the scope of the invention.
MATERIALS AND METHODS
Luminy® LX575 grade of PLA from Total-Corbion was used. Its properties are: Melt Flow Index (MFI)=8 g/10 min at 210°C, 2.16 kg; L-isomer content=98%; Melting temperature (Tm)=160-170°C; and glass transition temperature (Tg)=55-60. PLA/CaCO3 filler masterbatch compound (B1MC70) supplied by Konspec Speciality Poly Products Private Limited, Mangalore (India) were used.
The PLA flat tape yarn manufacturing and subsequent circular weaving into the fabric was carried out at Technical Training and Research Center, Kanpur (India). Lorex E75B800 tape extrusion line suited form PP/PE was used for the trials. Fabrics were woven on LSL 6 & Nova 6 machines. Example 1:
PLA polymer was added to the extruder, melted, extruded into a film which was quenched in a water bath maintained at 30-35°C. The film coming out of the bath was very brittle and had wrinkles on its surface. The brittleness of the film prevented its transfer from the bath to the tape slitter and subsequent slitting into tapes. The film

had a tendency to tear easily and couldn't be slit into tapes. This prevented processing through subsequent stages of hot stretching, annealing, winding, etc. Despite optimization of polymer throughput, air gap i.e. vertical distance between die and water bath, film take up speed, etc. the brittleness couldn't be reduced/eliminated. Example-II:
PLA polymer was added to the extruder, melted, extruded into a film which was quenched in a water bath maintained at 60°C. The modification in Example II allowed the slitting of film into the tapes, which could be stretched (1:5 stretch ratio) through hot air oven at a temperature of 100°C, annealed and wound. The un-stretched tapes/film from Example I were brittle, had very low tensile properties (<1 gpd) and did not have enough strength for subsequent step of weaving into fabrics. On the other hand, as described in Table II, the tensile properties of the PLA tapes obtained through modified process were improved significantly.

Hot Water
Trial PLA PLA/CaCO3 Draw Stretch Bath Film

Filler Ratio Temp Temp Brittleness
(°C) (°C)
I 100% - 1:5 100 30-35°C YES
II 91.3% 8.7% 1:5 100 55-60°C NO
Table 1
The improvement in tensile properties allowed the conversion of these tapes into woven fabric on a circular weaving machine into a fabric with adequate strength and other characteristics for packaging applications. The characteristics of the tape yarn are summarized in Table 2.

PLA
Tapes Denier Strength (kg) Tenacity (gpd) Elongation (%)
Example - - <1 -

I
Example II 1450 2.48 1.7 19.1
Table 2
Effect of hot stretch temperature and draw ration on tensile properties of the tape yarn tape yarn manufacturing (PLA= 90%, CaCO3=10%) is shown in Table 3

Draw Ratio Hot Stretch Temp (°C) Denier Tenacity (gpd) Elongation
1:3 110 867 0.71 22.73
1:4 110 949 0.87 23.91
1:5 110 442 1.15 14.64
1:6 110 311 1.89 18.48
1:7 125 393 1.79 13.42
1:8 140 327 1.51 18.95
Table 1
As a result of process of current invention tape yarn can be prepared from PLA with desired tenacity & elongation suitable to be converted into woven fabric for packaging. These PLA based fabrics can be used for the bulk packaging of grain, food items and industrial commodities.
The foregoing description of the invention is illustrative and explanatory thereof. Various modifications will become apparent to those skilled in the art in view of the present disclosure. It is intended that all such variations which fall within the scope and spirit of the appended claims be embraced thereby.

Claims We Claim:
1) A process of preparing a polylactic acid tape yarn, comprising:
a) melting a blend of polylactic acid and at least one filler material in an extruder;
b) extruding said blend of molten polylactic acid and filler through a die to obtain a film of polylactic acid;
c) passing said film of polylactic acid through water at a temperature of about 40oC to 90oC;
d) splitting said film of polylactic acid in to tape; and
e) stretching the tape in a hot air oven to yield polylactic acid tape yarn.

2) The process as claimed in claim 1, wherein melting of step (a) is carried out at a temperature in the range of 150-180oC.
3) The process as claimed in claim 1, wherein said filler material is selected from a group consisting of calcium carbonate, talc, silicates, clay, preferably calcium carbonate.
4) The process as claimed in claim 1, wherein said filler is in the range of 5-15 % (W/W).
5) The process a claimed in claim 1, wherein stretching of step (e) is carried out at a temperature in the range of 90oC to 140oC
6) A polylactic tape yarn prepared by process as claimed in claim 1, having elongation at break in the range of 8-30%.
7) A polylactic tape yarn prepared by process as claimed in claim 1, having a draw ratio in the range of 1:3 to 1:8.