Product overview
Paper-grade sodium CMC is used for surface sizing, in coating colours and at the wet end. It improves surface strength and printability and helps control the flow of coating colours.
Grades and specification
| Property | GAC-CMC-1 | GAC-CMC-2 | GAC-CMC-3 |
|---|---|---|---|
| Viscosity, 2% (mPa·s) | 10–50 | 100–200 | 5–10 |
| Purity, % | 40 ± 2 | 40 ± 2 | 80 |
| Degree of substitution | ≥ 0.6 | ≥ 0.6 | ≥ 0.8 |
| pH | 8–10 | 8–10 | 6–8 |
| Chloride (NaCl) | ≤ 5% | ≤ 7% | ≤ 7% |
| Moisture | ≤ 10% | ≤ 10% | ≤ 10% |
Typical dosage 0.3–1.5%, depending on the application. Values are from our current product data. Confirm the exact grade and limits with the TDS and the COA of the lot you test.
Applications
- Surface sizing: surface strength, ink holdout and smoothness
- Coating colours: water retention and flow of pigment dispersions
- Wet end: retention and wet strength support
Where CMC goes in a paper machine
| Position | Grade | Effect |
|---|---|---|
| Size press | GAC-CMC-1, GAC-CMC-2 | Surface strength, lower dusting, better ink holdout |
| Coating colour | GAC-CMC-3 | Water retention, viscosity control, smoother coating |
| Wet end | GAC-CMC-1 | Dry strength and fibre bonding |
In coating colours, CMC controls how fast water drains from the colour into the base paper. Good water retention gives a more even coat weight and fewer streaks at high machine speeds.
How to choose a grade
Low-viscosity, high-purity grades (GAC-CMC-3) suit coating colours; GAC-CMC-1 and -2 are cost-effective for surface sizing.
Packing and documents
25 kg multi-wall paper bags with an inner PE liner. Other packing is agreed per order. TDS, SDS and a representative COA are available for every grade, and each lot ships with its COA. Request documents or a sample.
Download (2026 revision): Technical data sheet (TDS, PDF) · Safety data sheet (SDS, PDF)
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FAQ
Can CMC replace part of the starch in sizing?
Often yes, at a low addition. Run a size-press trial and compare surface strength and printability.
Can CMC be used with starch at the size press?
Yes. CMC is commonly added to starch size to raise surface strength and film quality at a low addition.
Which viscosity for coating colours?
Low-viscosity grades (5–50 mPa·s at 2%) are preferred so the colour stays runnable at high solids.