JPH0367084B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermofusible material packaging bag. More specifically, the present invention relates to a packaging bag for a heat-melting substance made of a specific ethylene/α-olefin copolymer. Waxes such as parafin waxes, various sealing materials such as sealants for preventing rainwater leakage on the roofs of buildings, heat-melting road marking paints, asphalts, etc., are designed to be melted before use. The various materials required are used in many industrial fields. These heat-melting substances are sold commercially packed in packaging bags made of kraft paper, polyvinyl chloride resin, high-pressure low-density polyethylene resin, or the like. These heat-melting substances are used after being melted in a heating melting tank, kneader, or other suitable means. When using these heat-melting substances, it is difficult to remove the contents from the bag and to dispose of the bulky empty bag, which requires labor, effort, and expense. Furthermore, it was not favorable from the viewpoint of effective use of waste and resource conservation. As a way to solve the above-mentioned difficulties,
Publication No. 2228, Special Publication No. 52-48138, Special Publication No. 1987
-48019 and Japanese Patent Application Laid-Open No. 57-204868,
Ethylene vinyl acetate copolymer or ethylene-ethyl acrylate copolymer or mixture of polyethylene and ethylene-vinyl acetate copolymer or mixture of polyethylene, ethylene-acrylate copolymer and ethylene-vinyl acetate copolymer or linear low Density polyethylene or a mixture of linear low density polyethylene and ethylene-vinyl acetate copolymer, or a mixture of linear low density polyethylene and ethylene-acrylate copolymer, or linear low density polyethylene, ethylene-vinyl acetate copolymer and ethylene- It has been proposed that a bag made of a mixture of acrylate copolymers is filled with road marking paint as a heat-melting substance, and the bag is placed in a melting device to be heated and melted for use. However, when such packaging bags are used,
Road marking paints have a problem of high melt viscosity and clumping when heated and melted. Therefore, if the vinyl acetate or acrylate content in the packaging bag is further increased to about 7% by weight or more, the above-mentioned problem will be solved, but if the vinyl acetate or acrylate content is increased, the bag may become weak or the bag may become stuck tightly. This has the disadvantage that the workability of storing the paint in the bag is reduced. JP-A-57-204868 describes the use of packaging bags made of linear low-density polyethylene produced by ionic polymerization under medium and low pressures, which reduces the above-mentioned problems, but it The stiffness, toughness, heat sealing strength, heat resistance, printability of the packaging bag surface, and dispersibility into the contents of the packaging bag were not always satisfactory. The present invention relates to a heat-fusible substance packaging bag made of a specific ethylene/α-olefin copolymer, which has been recommended for the purpose of eliminating the above-mentioned drawbacks. That is, the present invention provides the following (a) obtained by copolymerizing ethylene and α-olefin in the presence of a catalyst consisting of a solid catalyst component containing at least magnesium and titanium and an organoaluminum compound.
The present invention relates to a packaging bag for a heat-fusible substance made of an ethylene/α-olefin copolymer having the properties described in (d). (a) Melt index is 0.01 to 100g/10min,
Preferably 0.03-10g/10min, (b) Density 0.860-0.910g/cm ³ , preferably 0.880
~0.9210 g/cm ³ , (c) The maximum peak temperature (Tm) in differential scanning calorimetry (DSC) is 100°C or higher, preferably 110°C or higher, (d) Boiling n-hexane insoluble matter is 10% by weight % or more, preferably 30-97% by weight. The ethylene/α-olefin copolymer used in the present invention must satisfy all of the above conditions (a) to (d). [Condition (a)] First, (a) melt index (JIS K6760)
If it is less than 0.01g/10min, film forming becomes difficult and a packaging bag cannot be obtained. On the other hand, 100g/
If it exceeds 10 min, the dart impact strength and pull strength will decrease, making it impossible to obtain a durable bag. [Condition (b)] If the density (JIS K6760) in (b) is less than 0.860 g/cm ³ , the bag will be too soft and lack strength, and the yield modulus, which is particularly related to waist strength, will decrease. . Furthermore, if the density exceeds 0.910 g/cm ³ , the dispersibility in heat-fusible substances decreases. [Condition (c)] The maximum peak temperature (Tm) measured by DSC in (c) is a value that correlates with the crystal form, and is particularly related to the heat sealability and heat resistance of the packaging bag of the present invention. Tm
If the temperature is less than 100°C, the bag will have poor heat resistance, and the packaging bag will melt and collapse when heated and filled with a heat-melting substance. [Condition (d)] Next, the boiling n-hexane insoluble portion in (d) is a guideline for the proportion of the amorphous portion and the content of low molecular weight components, and the insoluble portion is less than 10% by weight. In some cases, the amorphous portion and low molecular weight components increase, resulting in a decrease in strength, the stiffness of the bag, a decrease in heat resistance, and blocking that occurs, making it difficult to open the bag. Disadvantages arise such as reduced dispersibility in heat-fusible substances, especially wax. The method for measuring the boiling n-hexane insoluble matter and DSC in the present invention is as follows. [Measurement method for boiling n-hexane insoluble matter] A sheet with a thickness of 200 μm was formed using a heat press, and three sheets of 20 mm x 30 mm in length and width were cut from the sheet, and the sheets were placed in a double-tube Sotsukurray extractor. Extraction is carried out using boiling n-hexane for 5 hours. After taking out the n-hexane insoluble matter and vacuum drying (7 hours under vacuum, 50° C.), the boiling n-hexane insoluble matter is calculated using the following formula. Boiling n-hexane insoluble content (weight %) = Extracted sheet weight / unextracted sheet weight x 100 (weight %) [Measurement method by DSC] Approximately 5 mg of material was accurately weighed from a 100 μm thick hot press-molded film. The sample was set in a DSC device, heated to 170°C, held at that temperature for 15 minutes, and then cooled to 0°C at a cooling rate of 2.5°C/min.
Next, from this state, increase the temperature to 170°C at a rate of 10°C/min.
Measurement is performed by raising the temperature to . The temperature at the top of the maximum peak that appeared during the temperature increase from 0°C to 170°C is defined as Tm. The ethylene/α-olefin copolymer of the present invention can exhibit desired performance by satisfying all of the above-mentioned properties. The α-olefin copolymerized with ethylene has 3 to 12 carbon atoms. Specifically, propylene,
Butene-1, 4-methylpentene-1, hexene-1, octene-1, decene-1, dodecene-1
etc. can be mentioned. Particularly preferred among these are propylene and butene-1. The α-olefin content in the ethylene-α-olefin copolymer is preferably 5 to 40 mol%. Below, ethylene used in the present invention and α-
A method for producing an olefin copolymer will be explained. First, the catalyst system used is a combination of a solid catalyst component containing at least magnesium and titanium with an organic aluminum compound, and examples of the solid catalyst component include magnesium metal, magnesium hydride, magnesium carbonate, magnesium oxide, magnesium chloride, etc. , also silicon,
Double salts, double oxides, carbonates, chlorides, or hydroxides containing metals selected from aluminum and calcium and magnesium atoms, and furthermore, these inorganic solid compounds can be used as oxygen-containing compounds, sulfur-containing compounds, and aromatic compounds. Examples include those in which a titanium compound is supported by a known method on an inorganic solid compound containing magnesium, such as one treated or reacted with a hydrocarbon or halogen-containing substance. Examples of the above oxygen-containing compounds include organic oxygen-containing compounds such as water, alcohol, phenol, ketone, aldehyde, carboxylic acid, ester, polysiloxane, and acid amide, and inorganic oxygen-containing compounds such as metal alkoxides and metal oxychlorides. can be exemplified. Examples of sulfur-containing compounds include thiol,
Examples include organic sulfur-containing compounds such as thioethers, and inorganic sulfur compounds such as sulfur dioxide, sulfur trioxide, and sulfuric acid. As aromatic hydrocarbons,
benzene, toluene, xylene, anthracene,
Examples include various monocyclic and polycyclic aromatic hydrocarbon compounds such as phenanthrene. Examples of the halogen-containing substance include compounds such as chlorine, hydrogen chloride, metal chlorides, and organic halides. Examples of the titanium compound include titanium halogen compounds, alkoxy halides, alkoxides, and halogenated oxides. As the titanium compound, a tetravalent titanium compound and a trivalent titanium compound are suitable. Specifically, as a tetravalent titanium compound, the general formula Ti(OR)nX _4-o (here R
represents an alkyl group, aryl group or aralkyl group having 1 to 20 carbon atoms, and X represents a halogen atom.
n is 0≦n≦4. ) are preferred, and titanium tetrachloride, titanium tetrabromide, titanium tetraiodide, monomethoxytrichlorotitanium, dimethoxydichlorotitanium, trimethoxymonochlorotitanium, tetramethoxytitanium, monoethoxytrichlorotitanium, diethoxydichlorotitanium, Triethoxymonochlorotitanium, tetraethoxytitanium, monoisopropoxytrichlorotitanium, diisopropoxydichlorotitanium, triisopropoxymonochlorotitanium, tetraisopropoxytitanium, monobutoxytrichlorotitanium, dibutoxydichlorotitanium, monopentoxytrichlorotitanium, monophenol Examples include citrichlorotitanium, diphenoxydichlorotitanium, triphenoxymonochlorotitanium, and tetraphenoxytitanium. Examples of trivalent titanium compounds include titanium trihalides obtained by reducing titanium tetrahalides such as titanium tetrachloride and titanium tetrabromide with hydrogen, aluminum, titanium, or metals from group ~ of the periodic table and organometallic compounds. Can be mentioned. Further, it has the general formula Ti(OR)mX _4-n (where R represents an alkyl group, aryl group, or aralkyl group having 1 to 20 carbon atoms, and X represents a halogen atom. m satisfies 0<m<4). Examples include trivalent titanium compounds obtained by reducing a tetravalent alkoxy titanium halide represented by ) with an organometallic compound of a group metal of the periodic table. Among these titanium compounds, tetravalent titanium compounds are particularly preferred. Specific examples of these catalysts include, for example, the MgO-RX-TiCl ₄ system (Japanese Patent Publication No. 51-3514), the Mg-SiCl ₄ -ROH-TICl ₄ system (Japanese Patent Publication No. 1983-3514),
23864), MgCl ₂ −Al(OR) ₃ −TiCl ₄ system (Japanese Patent Publication No. 51-152, Japanese Patent Publication No. 52-15111),
MgCl ₂ −SiCl ₄ −ROH−TiCl ₄ system (Japanese Patent Application Laid-open No. 1983
106581), Mg(OOCR) ₂ −Al(OR) ₃ −TiCl ₄
system (Special Publication No. 52-11710), Mg−POCl ₃ −
TiCl ₄ system (Special Publication No. 153/1983), MgCl ₂ −
AlOCl-TiCl ₄ system (Special Publication No. 54-15316),
MgCl ₂ −Al(OR)nX ₃ −n−Si(OR′)mX _4-n −
Preferably, a solid catalyst component such as TiCl ₄ (Japanese Unexamined Patent Publication No. 56-95909) (in the above formula, R and R' are organic residues and X is a halogen atom) is combined with an organic aluminum compound. This is an example of a catalyst system. Examples of other catalyst systems include solid catalyst components such as
An example is a catalyst system in which a reaction product of an organomagnesium compound such as a so-called Grignard compound and a titanium compound is used in combination with an organoaluminum compound. Examples of organomagnesium compounds include general formula RMgX,
Organomagnesium compounds such as R ₂ Mg, RMg (OR) (where R is an organic residue having 1 to 20 carbon atoms,
represents a halogen) and their ether complexes, and these organomagnesium compounds can be further combined with other organometallic compounds such as organosodium, organolithium, organopotassium, organoboron,
Those modified by adding various compounds such as organic cowsium and organic zinc can be used. Specific examples of these catalyst systems include, for example:
RMgX-TiCl ₄ system (Special Publication No. 50-39470),
RMgX-Phenol-TiCl ₄ system (Special Publication 1984-
12953), RMgX-halogenated phenol-TiCl ₄ system (Japanese Patent Publication No. 54-2954), RMgx-
Examples include combinations of organoaluminium compounds with solid catalyst components such as CO ₂ -TiCl ₄ (JP-A-57-73009). In addition, as an example of another catalyst system, a solid substance obtained by contacting an inorganic oxide such as SiO ₂ or Al ₂ O ₃ with a solid catalyst component containing at least magnesium and titanium is used as a solid catalyst component, An example of this can be combined with an organoaluminum compound. As an inorganic oxide
In addition to SiO ₂ and Al ₂ O ₃ , CaO, B ₂ O ₃ , SnO ₂ and the like can be used, and double oxides of these oxides can also be used without any problem. Any known method can be used to bring these various inorganic oxides into contact with the solid catalyst component containing magnesium and titanium. That is, a method of reacting in the presence or absence of an inert solvent at a temperature of 20 to 400°C, preferably 50 to 300°C for usually 5 minutes to 20 hours, a method of co-pulverization, or a combination of these methods as appropriate. The reaction may be carried out by Specific examples of these catalyst systems include, for example, the SiO ₂ -ROH-MgCl ₂ -TiCl ₄ system (Japanese Patent Application Laid-Open No.
47407), _SiO2 -R-O-R'-MgO- _AlCl3
−TiCl ₄ system (JP-A-57-187305), SiO ₂ −
MgCl ₂ −Al(OR) ₃ −TiCl ₄ −Si(OR′) ₄ series (JP-A-Sho
58-21405) (in the above formula, R and R' represent hydrocarbon residues), in combination with an organoaluminum compound. In these catalyst systems, a titanium compound can be used as an adduct with an organic carboxylic acid ester, or the above-described magnesium-containing inorganic solid compound can be used after being brought into contact with an organic carboxylic acid ester. Moreover, there is no problem in using an organoaluminum compound as an adduct with an organic carboxylic acid ester. Furthermore, in all cases it is also possible to use catalyst systems prepared in the presence of organic carboxylic acid esters without any problems. Here, various aliphatic, alicyclic, and aromatic carboxylic esters are used as the organic carboxylic ester, and aromatic carboxylic esters having 7 to 12 carbon atoms are preferably used. Specific examples include alkyl esters of benzoic acid, anisic acid, toluic acid, such as methyl and ethyl. A specific example of an organoaluminum compound to be combined with the above-mentioned solid catalyst component is the general formula
R ₃ Al, R ₂ AlX, RAlX ₂ , R ₂ AlOR, RAl(OR)
An organoaluminum compound of X and R ₃ Al ₂ X ₃ (where R is an alkyl group, aryl group or aralkyl group having 1 to 20 carbon atoms,
(R may be the same or different) Compounds represented by triethylaluminum, triisobutylaluminum, trihexylaluminum, trioctylaluminum, diethylaluminum chloride, diethylaluminum ethoxide, ethylaluminum sesquichloride, and mixtures thereof are preferred. etc. can be mentioned. The amount of organoaluminum compound used is not particularly limited, but is usually 0.1 to 1000% of the titanium compound.
Molar times can be used. In addition, by bringing the above-mentioned catalyst system into contact with an α-olefin and then using it in the polymerization reaction, the polymerization activity can be greatly improved, and the system can be operated more stably than when untreated. Various α-olefins can be used at this time, but α-olefins having 3 to 12 carbon atoms are preferred, and α-olefins having 3 to 8 carbon atoms are more preferred. Examples of these α-olefins include propylene, butene-
Examples include 1, pentene-1, 4-methylpentene-1, hexene-1, octene-1, decene-1, dodecene-1, and mixtures thereof. The temperature and time during contact between the catalyst system and the α-olefin can be selected within a wide range, for example, the contact treatment can be carried out at 0 to 200°C, preferably 0 to 110°C, for 1 minute to 24 hours. α to contact
-The amount of olefin can be selected from a wide range, but usually
It is desirable to treat 1 g of the solid catalyst component with 1 g to 50,000 g, preferably 5 g to 30,000 g of α-olefin, and react with 1 g to 500 g of α-olefin per 1 g of the solid catalyst component. At this time, the pressure at the time of contact can be arbitrarily selected, but it is usually desirable to contact under a pressure of -1 to 100 kg/cm ² ·G. During the α-olefin treatment, the entire amount of the organoaluminum compound used may be combined with the solid catalyst component and then brought into contact with the α-olefin, or a part of the organoaluminum compound used may be combined with the solid catalyst component. After combining with α
- The polymerization reaction may be carried out by contacting with the olefin and adding the remaining organoaluminum compound separately during the polymerization. In addition, there is no problem even if hydrogen gas coexists during the contact between the catalyst system and α-olefin.
Further, there is no problem even if other inert gases such as nitrogen, argon, helium, etc. coexist. The polymerization reaction is carried out in the same manner as the polymerization reaction of olefins using ordinary Ziegler type catalysts. That is, all reactions are carried out in a gas phase, in the presence of an inert solvent, or using the monomer itself as a solvent in a state in which oxygen, water, etc. are substantially excluded. The polymerization conditions for olefin are temperatures of 20 to 300℃, preferably 40 to 200℃.
℃, and the pressure is normal pressure to 70 kg/cm ² ·G, preferably 2 kg/cm ² ·G to 60 kg/cm ² ·G.
Although the molecular weight can be controlled to some extent by changing polymerization conditions such as polymerization temperature and catalyst molar ratio, it is effectively carried out by adding hydrogen to the polymerization system. Of course, a two-step or more multi-step polymerization reaction with different polymerization conditions such as hydrogen concentration and polymerization temperature can be carried out without any problem. As described above, specific ethylene and It was completely unexpected and surprising that a thermofusible material packaging bag with excellent properties could be provided using an olefin copolymer. The ethylene/α-olefin copolymer of the present invention is clearly distinguished from the ethylene/α-olefin copolymer obtained by using one containing vanadium as a solid catalyst component. Even if the monomers constituting the copolymer are the same and the density is the same, DSC
The copolymer of the present invention has a higher Tm than that of the copolymer of the present invention, and the copolymer of the present invention has a boiling n-hexane insoluble content of 10% by weight or more, whereas the latter has no insoluble matter or has a very small amount. be. Due to these differences in the strong polymers themselves, when used for packaging bags for heat-fusible substances, the copolymers of the present invention have superior heat resistance and strength as well as heat resistance compared to the latter. Excellent balance of performance required for fusible substance packaging bag applications. Furthermore, unlike titanium, vanadium present in the copolymer as a catalyst residue poses a toxicity problem, so a catalyst removal process is essential.However, when titanium is used as in the present invention, the toxicity of the catalyst residue becomes a problem. The copolymer of the present invention, which uses a highly active catalyst in combination with a magnesium carrier, is extremely economical because a catalyst removal step is not required. The product of the present invention solves all of the drawbacks of conventional high-pressure low-density polyethylene and ethylene-vinyl acetate copolymers, and achieves the required performance in a well-balanced manner. The meltable substance that is the object of the present invention is a substance that melts when heated. Specifically, waxes, asphalts, petroleum resins, rosins, various thermoplastic resins, mixtures thereof, or combinations of these with pigments, fillers, softeners, plasticizers, liquid resins, light reflecting balls, etc. Typical examples of mixtures and specific uses thereof include heat-melting road marking paints and sealing materials for preventing rainwater leakage from building roofs or rooftops. When the heat-melting substance is used, it is placed in a bag in a melting device and melted. Forms of use include those in which it is applied immediately after melting, such as sealing materials and road marking paints, forms in which other materials are added to and mixed with the molten heat-melting substance, and forms in which the heat-meltable substance and other materials are mixed. There are forms in which they are simultaneously melted or heated and mixed. In addition to the various heat-melting substances mentioned above, other materials include pigments, fillers, softeners, plasticizers, liquid resins, light reflecting balls, rubbers, inorganic substances, etc., but are not particularly limited to heat-melting substances. It is a substance added to impart certain properties. The packaging bag of the present invention can be applied to any of these usage forms. The characteristics of the heat-fusible substance packaging bag made of the specific ethylene/α-olefin copolymer described above are as follows. (1) When the packaging bag is heat-fused, the various heat-melting substances mentioned above or other materials mixed with the heat-melting substances are uniformly dispersed without clumping, and have good fluidity. manifest. (2) The packaging bag is strong and can be easily filled with heat-melting substances. The strength of the waist is expressed by the yield modulus in terms of film properties. The yield modulus of the ethylene/α-olefin copolymer according to the present invention is equivalent to that of a strong ethylene-vinyl acetate polymer with a vinyl acetate content of about 15% by weight, and has sufficient stiffness. has. A strong ethylene-vinyl acetate polymer having a vinyl acetate content of about 15% by weight is not suitable for use in the present invention because of its low dispersibility in heat-fusible substances. In addition, the low densities known in this application field have superior yield modulus compared to polyethylene and ethylene-ethyl acrylate copolymers. (3) Sufficient durability when used as a packaging bag. Durability is expressed by dart impact strength. The dart impact strength of the film made of the ethylene/α-olefin copolymer according to the present invention is compared with that of ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, and low-density polyethylene, which are known in this application field. And it's excellent. (4) Good heat sealability. In the case of synthetic resin bags, sealing after filling the bag with contents is usually performed by heat sealing. When a bag filled with contents is distributed as a product, in order to prevent the contents from being scattered due to destruction of the bag, not only the bag itself must be strong, but also the heat-sealed part must be sufficiently strong. be done.
The heat seal strength of the film made of the ethylene/α-olefin copolymer according to the present invention is compared with that of ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, and low-density polyethylene, which are known in this application field. This is sufficient. (5) When filling a bag with a heat-melting substance, the filling substance is not necessarily at room temperature, but may be at a considerably high temperature. In such cases, the raw material resin for the bag is required to have appropriate heat resistance. Since the ethylene/α-olefin copolymer according to the present invention is polymerized using a titanium-based catalyst, it has crystallinity and has a high Tm of 100°C or more, which is comparable to the ethylene-vinyl acetate copolymer known in this application field. It has superior heat resistance compared to copolymers, ethylene-ethylene acrylate copolymers, and low-density polyethylene. (6) In order to distribute the bag filled with the heat-melting substance as a product, it is necessary to perform various types of printing on the front and back surfaces of the bag. Printability is evaluated by the wetting tension of the resin film against the solvent. The wetting tension of the ethylene/α-olefin copolymer according to the present invention is at a level that provides sufficiently good printability. The present invention will be specifically explained below using Examples. The polymers used in Examples and Comparative Examples are as follows. Example 1 Copolymerization of ethylene and butene-1 using a solid catalyst component obtained from substantially anhydrous magnesium chloride, 1,2-dichloroethane and titanium tetrachloride and a catalyst consisting of triethylaluminum Ethylene-butene-1 copolymer. The ethylene content of this copolymer is 91.5 mol%, the melt index is 0.50 g/10 min, and the density is
0.904g/cm ³ , DSC maximum peak temperature 120.5℃,
The boiling n-hexane insoluble portion was 94% by weight. Example 2 An ethylene-propylene copolymer obtained by copolymerizing ethylene and propylene using a solid catalyst component obtained from substantially anhydrous magnesium chloride, anthracene and titanium tetrachloride and a catalyst consisting of triethylaluminum. The ethylene content of this copolymer is 81.5 mol%, the melt index is 1.0 g/min, and the density is 0.890.
g/cm ³ , the maximum peak temperature of DSC was 121.6°C, and the content insoluble in boiling n-hexane was 58% by weight. Comparative Example 1 High pressure low density polyethylene, melt index 1.0g/10min, density 0.923g/cm ³ . Comparative Example 2 Ethylene-vinyl acetate copolymer, melt index 1.0 g/10 min, density 0.928 g/cm ³ . Comparative Example 3 Ethylene-butene-1 copolymer obtained with vanadium catalyst, melt index 3.8 g/
10 min, density 0.887 g/cm ³ , maximum peak temperature of DSC 67.1°C, boiling n-hexane insoluble content 0.0%. Table 1 shows the physical properties of the above examples and comparative examples.
summarized in. 【table】

Claims (1)

[Claims] 1. The following (a) to (d) obtained by copolymerizing ethylene and α-olefin in the presence of a solid catalyst component containing at least magnesium and titanium and a catalyst consisting of an organoaluminum compound. A packaging bag for a heat-melting substance made of an ethylene/α-olefin copolymer with the following properties: (a) Melt index 0.01 to 100 g/10 min, (b) Density 0.860 to 0.910 g/cm ³ , (c) Differential scanning calorimetry The maximum peak temperature (Tm) measured by the measuring method (DSC) is 100°C or higher; (d) Boiling n-hexane insoluble content is 10% by weight or higher. 2. The heat-fusible substance packaging bag according to claim 1, wherein the α-olefin is an α-olefin having 3 to 12 carbon atoms. 3 The heat-melting substance is wax, a sealing material,
The heat-melt material packaging bag according to claim 1, characterized in that the bag is a heat-melt paint or asphalt.